Light is electromagnetic radiation that is visible to the human eye and allows us to see. The main sources of light are the sun and artificial lights like fire or electricity. We cannot see objects in the dark because light needs to reflect off objects and enter our eyes. The eyes contain a lens that focuses light onto the retina, where it is detected by light-sensitive cells and transmitted to the brain as visual information via the optic nerve. Care must be taken of our eyes through proper lighting, nutrition, and avoiding rubbing or direct viewing of bright lights.
1. Light travels in a straight line and can be reflected. When light hits a non-transparent object, it changes direction rather than passing through. The reflected light then reaches our eyes, allowing us to see objects.
2. Experiments can demonstrate the linear propagation of light using a laser, tubes, cardboard with holes, or observing dust particles in a beam of light. Light will only pass through holes that are aligned.
3. Shadows are formed when a light source is blocked by an object. A point light source will create a dark umbra shadow, while an extended source makes both a dark umbra and a faint penumbra shadow. Solar and lunar eclipses occur through the formation of shadows
Light travels in a straight line and can be reflected, refracted, or absorbed when it hits different materials and surfaces. Reflection occurs when light bounces off a surface like a mirror, following the laws of reflection. Refraction is when light changes direction as it passes from one medium to another, like from air to water. Lenses and curved mirrors can form real or virtual images by refracting or reflecting light rays. Prisms disperse white light into a spectrum due to refraction, demonstrating that light is made of different colors.
Light travels in straight lines from a source, such as the sun. When light hits an object, it can be reflected, absorbed, or pass through. Reflected light allows us to see objects, while absorbed light is what makes objects appear colored. Transparent materials allow light to pass through them, while opaque materials block light and cast shadows. The shape and size of shadows changes depending on the position of the light source and object. Lenses and mirrors can refract or reflect light to magnify or change its direction.
This document defines and provides examples of luminous and non-luminous objects, and describes the properties and behavior of light rays, shadows, reflection, refraction, color, and optical instruments like mirrors, prisms, and periscopes. Key terms discussed include transparent, translucent, and opaque materials; angles of incidence and reflection; real and virtual images; absorption and reflection of color; and how rainbows are formed by light refraction in water droplets.
This document summarizes key concepts about light, including:
1. Light travels in straight lines and can be reflected or refracted. The law of reflection states that the angle of incidence equals the angle of reflection.
2. Refraction occurs when light travels from one medium to another of different density, causing the light to bend and change speed. This is demonstrated through experiments with glass blocks.
3. Prisms disperse white light into a visible spectrum due to the different wavelengths of light being refracted different amounts.
4. Mirrors form virtual upright images that are laterally inverted from the object, as shown through ray diagrams. Shadows are formed when light is blocked by an opaque object.
Light refracts and reflects when moving between materials of different densities. Refraction causes light to bend when entering a denser medium, following Snell's law. Total internal reflection occurs when light hits a boundary at an angle greater than the critical angle, causing all light to reflect inside the denser medium rather than passing through.
1. Light travels in a straight line and can be reflected. When light hits a non-transparent object, it changes direction rather than passing through. The reflected light then reaches our eyes, allowing us to see objects.
2. Experiments can demonstrate the linear propagation of light using a laser, tubes, cardboard with holes, or observing dust particles in a beam of light. Light will only pass through holes that are aligned.
3. Shadows are formed when a light source is blocked by an object. A point light source will create a dark umbra shadow, while an extended source makes both a dark umbra and a faint penumbra shadow. Solar and lunar eclipses occur through the formation of shadows
Light travels in a straight line and can be reflected, refracted, or absorbed when it hits different materials and surfaces. Reflection occurs when light bounces off a surface like a mirror, following the laws of reflection. Refraction is when light changes direction as it passes from one medium to another, like from air to water. Lenses and curved mirrors can form real or virtual images by refracting or reflecting light rays. Prisms disperse white light into a spectrum due to refraction, demonstrating that light is made of different colors.
Light travels in straight lines from a source, such as the sun. When light hits an object, it can be reflected, absorbed, or pass through. Reflected light allows us to see objects, while absorbed light is what makes objects appear colored. Transparent materials allow light to pass through them, while opaque materials block light and cast shadows. The shape and size of shadows changes depending on the position of the light source and object. Lenses and mirrors can refract or reflect light to magnify or change its direction.
This document defines and provides examples of luminous and non-luminous objects, and describes the properties and behavior of light rays, shadows, reflection, refraction, color, and optical instruments like mirrors, prisms, and periscopes. Key terms discussed include transparent, translucent, and opaque materials; angles of incidence and reflection; real and virtual images; absorption and reflection of color; and how rainbows are formed by light refraction in water droplets.
This document summarizes key concepts about light, including:
1. Light travels in straight lines and can be reflected or refracted. The law of reflection states that the angle of incidence equals the angle of reflection.
2. Refraction occurs when light travels from one medium to another of different density, causing the light to bend and change speed. This is demonstrated through experiments with glass blocks.
3. Prisms disperse white light into a visible spectrum due to the different wavelengths of light being refracted different amounts.
4. Mirrors form virtual upright images that are laterally inverted from the object, as shown through ray diagrams. Shadows are formed when light is blocked by an opaque object.
Light refracts and reflects when moving between materials of different densities. Refraction causes light to bend when entering a denser medium, following Snell's law. Total internal reflection occurs when light hits a boundary at an angle greater than the critical angle, causing all light to reflect inside the denser medium rather than passing through.
Science8 Unit C Lightand Optics Section2 Lesson4 Mirrors Lensesand Refraction...Shorin
The document summarizes key concepts about light and optics from sections 2.3-2.5 of a textbook. It explains that curved mirrors can form real, inverted images by refracting light rays. Concave mirrors converge light to a focal point, while convex mirrors diverge light rays. It also discusses how the refraction of light through different materials like water and lenses can bend and focus light to form images. Hands-on activities and sample questions are provided to help students understand and demonstrate these optical phenomena.
Science8 Unit C Lightand Optics Section2 Lesson3 Raysand ReflectionShorin
Ray diagrams
Intensity of Light
Transparent
Translucent
Opaque
Luminous
Non-Luminous
Regular Reflection
Diffuse Reflection
Incident Rays
Plane Mirrors
Normal
Angle of Incidence
Angle of reflection
Interactive textbook ch 23 light and our worldtiffanysci
Ray diagrams can be used to represent the path of light waves as they interact with mirrors and lenses. There are three types of mirrors: plane mirrors form reversed virtual images, concave mirrors can form real or virtual images depending on the object's position, and convex mirrors always form smaller virtual images. Concave lenses only form virtual images while convex lenses can form real or virtual images depending on the object's distance from the lens.
Light travels in straight lines. Shadows are formed when light is blocked by an object. The size and shape of shadows can change depending on the position of the light source and object. Reflection of light allows us to see objects when light bounces off their surfaces and into our eyes. Common examples of reflection include mirrors, water surfaces, and other shiny materials.
This document provides an overview of concepts related to light, including what light is, reflection, refraction, and color. It begins with definitions of light and its properties like traveling in straight lines and at a high speed. Later sections discuss reflection, including the laws of reflection and materials that reflect light well or poorly. Refraction is then covered, including how light bends when changing mediums and the rules of refraction. Effects of refraction like apparent depth and how archer fish aim are also summarized. Activities and investigations related to these light topics are outlined to help teach the concepts.
This document discusses the properties and importance of light. It explains that there are two types of light: natural light from the sun, moon, stars, and fireflies, and artificial light created by humans like candles and light bulbs. Light travels very fast, is a form of energy that travels in waves, and can be reflected, refracted, or absorbed as it interacts with different materials and objects. The document also describes how vision works and how we see color depending on which wavelengths of light are reflected or absorbed by various surfaces.
1. The document provides instructions and objectives for science lessons on various topics including light and color, electricity, and forces.
2. Key concepts to be covered include the speed of light, reflection, refraction, dispersion of white light through a prism, and how rainbows are formed.
3. Students are asked to complete assignments, worksheets, and textbook questions to reinforce their understanding of these scientific principles.
Light can be produced through natural and artificial means. It exhibits properties of reflection, refraction, and wavelength. The human eye detects visible light and uses lenses and color-sensitive cells to form images and see color. Emerging technologies like LEDs and OLEDs use electricity to produce light through electroluminescence, while older light sources like incandescent and fluorescent bulbs work through heating and gas excitation. Proper understanding of light, vision, and lighting enables evaluation of their technological impacts.
Science8 Unit C Lightand Optics Section1 Lesson2 Optical DevicesShorin
The document summarizes the development of microscopes, telescopes, and other optical devices and how they contributed to the study of light and science. It describes how the first microscope was developed in the 1590s and improved over time. Telescopes were also developed in the 1600s allowing discoveries of astronomical objects. Microscopes use two lenses, an objective and eyepiece, to magnify objects, while telescopes magnify and collect light using mirrors or lenses. Developments in these optical devices advanced the understanding of light and vision.
Slide that I created to support teaching science to my lower secondary student (Grade 7). The topic is Ray Model of Light. Some contents (pics and videos) are not mine. Hope it is useful for all teacher around the globe.
Our main source of light is the sun. Light is a form of energy that allows us to see and is essential for life on Earth. Plants use sunlight for photosynthesis to produce food and oxygen. Sunlight also warms the Earth and drives weather patterns through heating and wind. Too much sunlight can damage skin and eyes, so protection is needed with long exposure.
The document discusses the history and development of physically-based rendering techniques. It begins with an overview of early theories of light and vision from ancient Greece. It then covers major advances in understanding light, reflection, and refraction from the 17th-20th centuries. The document outlines the Blinn-Phong shading model developed in 1977 as one of the first real-time rendering techniques. While it represented an improvement over prior methods, it had limitations like not conserving energy and being unable to model complex materials realistically. The talk will cover modern physically-based rendering theory and practice.
Specular reflection occurs off smooth surfaces at defined angles, while diffuse reflection scatters light in many directions from rough surfaces. The law of reflection states that the angle of incidence equals the angle of reflection. A flat mirror produces virtual images through reflection, where the image is reversed from the object.
Light travels in straight lines at a speed of around 300,000 kilometres per second, much faster than sound. We see objects because they reflect light into our eyes. Shadows are formed when light is blocked by an object. Light reflects off surfaces at the same angle it hits them, following the law of reflection. White light is made up of the colors of the rainbow which can be split and recombined.
This document discusses how vision works and the science of reflection. It explains that light reflects off shiny, smooth surfaces like mirrors, while it scatters off rough surfaces. When light hits different materials, it may reflect, scatter, or refract. Reflection causes light to bounce back at the same angle, while refraction bends the light. Experiments are described to observe reflection using mirrors and the bending of light when it passes through water or other transparent materials.
This document discusses various sources of light and how light interacts with objects. It covers how light travels from sources to our eyes, how we see objects that are not light sources via light reflecting off of them, and how reflection works with both rough and shiny surfaces. It also explores color, how white light is composed of many colors, and how combining colors of light produces new colors.
The document discusses several key properties of light, including:
- Reflection - Light bounces off surfaces at the same angle it hits.
- Refraction - Light bends as it passes from one medium to another, changing speed. The degree of bending depends on the medium's index of refraction.
- Interference - When two light waves meet, they can constructively or destructively interfere based on how their crests and troughs align.
It explores light's dual nature as both a wave and particle, demonstrated through experiments like Young's double-slit experiment showing light's wave-like interference patterns, and the photoelectric effect showing its particulate properties.
1) Light travels in straight lines and is a form of energy that travels much faster than sound.
2) We see objects because they reflect light into our eyes, and shadows are formed when light is blocked.
3) Mirrors come in plane, convex, and concave shapes and can form real or virtual images depending on their shape and whether the light rays actually meet or appear to meet.
Light travels in straight lines and can be reflected or refracted. There are three types of materials: transparent, translucent, and opaque. Shadows are formed when an object blocks light. The length and shape of a shadow depends on the position of the light source and object. An experiment was conducted to determine which material - transparent plastic, tissue paper, or black paper - makes the darkest shadow. Black paper produced the darkest shadow because it is opaque and does not let any light pass through.
The document contains information about a student's foundation portfolio for media including a chosen brief to design the front cover and contents page of a school/college magazine. It includes sample front covers and contents pages of magazines following conventions such as mastheads, cover lines, and images. It also provides representations of celebrities on magazine covers analyzing aspects like costumes, poses, and expressions to engage readers. Ideas and plans are proposed for the student's own magazine cover and contents page design incorporating conventional elements.
Cinco estudiantes realizaron trabajos prácticos, exámenes y obtuvieron promedios. Tres estudiantes aprobaron con promedios entre 7.0 y 8.3, mientras que uno reprobó con 5.3 y otro suspendió con 4.7.
Science8 Unit C Lightand Optics Section2 Lesson4 Mirrors Lensesand Refraction...Shorin
The document summarizes key concepts about light and optics from sections 2.3-2.5 of a textbook. It explains that curved mirrors can form real, inverted images by refracting light rays. Concave mirrors converge light to a focal point, while convex mirrors diverge light rays. It also discusses how the refraction of light through different materials like water and lenses can bend and focus light to form images. Hands-on activities and sample questions are provided to help students understand and demonstrate these optical phenomena.
Science8 Unit C Lightand Optics Section2 Lesson3 Raysand ReflectionShorin
Ray diagrams
Intensity of Light
Transparent
Translucent
Opaque
Luminous
Non-Luminous
Regular Reflection
Diffuse Reflection
Incident Rays
Plane Mirrors
Normal
Angle of Incidence
Angle of reflection
Interactive textbook ch 23 light and our worldtiffanysci
Ray diagrams can be used to represent the path of light waves as they interact with mirrors and lenses. There are three types of mirrors: plane mirrors form reversed virtual images, concave mirrors can form real or virtual images depending on the object's position, and convex mirrors always form smaller virtual images. Concave lenses only form virtual images while convex lenses can form real or virtual images depending on the object's distance from the lens.
Light travels in straight lines. Shadows are formed when light is blocked by an object. The size and shape of shadows can change depending on the position of the light source and object. Reflection of light allows us to see objects when light bounces off their surfaces and into our eyes. Common examples of reflection include mirrors, water surfaces, and other shiny materials.
This document provides an overview of concepts related to light, including what light is, reflection, refraction, and color. It begins with definitions of light and its properties like traveling in straight lines and at a high speed. Later sections discuss reflection, including the laws of reflection and materials that reflect light well or poorly. Refraction is then covered, including how light bends when changing mediums and the rules of refraction. Effects of refraction like apparent depth and how archer fish aim are also summarized. Activities and investigations related to these light topics are outlined to help teach the concepts.
This document discusses the properties and importance of light. It explains that there are two types of light: natural light from the sun, moon, stars, and fireflies, and artificial light created by humans like candles and light bulbs. Light travels very fast, is a form of energy that travels in waves, and can be reflected, refracted, or absorbed as it interacts with different materials and objects. The document also describes how vision works and how we see color depending on which wavelengths of light are reflected or absorbed by various surfaces.
1. The document provides instructions and objectives for science lessons on various topics including light and color, electricity, and forces.
2. Key concepts to be covered include the speed of light, reflection, refraction, dispersion of white light through a prism, and how rainbows are formed.
3. Students are asked to complete assignments, worksheets, and textbook questions to reinforce their understanding of these scientific principles.
Light can be produced through natural and artificial means. It exhibits properties of reflection, refraction, and wavelength. The human eye detects visible light and uses lenses and color-sensitive cells to form images and see color. Emerging technologies like LEDs and OLEDs use electricity to produce light through electroluminescence, while older light sources like incandescent and fluorescent bulbs work through heating and gas excitation. Proper understanding of light, vision, and lighting enables evaluation of their technological impacts.
Science8 Unit C Lightand Optics Section1 Lesson2 Optical DevicesShorin
The document summarizes the development of microscopes, telescopes, and other optical devices and how they contributed to the study of light and science. It describes how the first microscope was developed in the 1590s and improved over time. Telescopes were also developed in the 1600s allowing discoveries of astronomical objects. Microscopes use two lenses, an objective and eyepiece, to magnify objects, while telescopes magnify and collect light using mirrors or lenses. Developments in these optical devices advanced the understanding of light and vision.
Slide that I created to support teaching science to my lower secondary student (Grade 7). The topic is Ray Model of Light. Some contents (pics and videos) are not mine. Hope it is useful for all teacher around the globe.
Our main source of light is the sun. Light is a form of energy that allows us to see and is essential for life on Earth. Plants use sunlight for photosynthesis to produce food and oxygen. Sunlight also warms the Earth and drives weather patterns through heating and wind. Too much sunlight can damage skin and eyes, so protection is needed with long exposure.
The document discusses the history and development of physically-based rendering techniques. It begins with an overview of early theories of light and vision from ancient Greece. It then covers major advances in understanding light, reflection, and refraction from the 17th-20th centuries. The document outlines the Blinn-Phong shading model developed in 1977 as one of the first real-time rendering techniques. While it represented an improvement over prior methods, it had limitations like not conserving energy and being unable to model complex materials realistically. The talk will cover modern physically-based rendering theory and practice.
Specular reflection occurs off smooth surfaces at defined angles, while diffuse reflection scatters light in many directions from rough surfaces. The law of reflection states that the angle of incidence equals the angle of reflection. A flat mirror produces virtual images through reflection, where the image is reversed from the object.
Light travels in straight lines at a speed of around 300,000 kilometres per second, much faster than sound. We see objects because they reflect light into our eyes. Shadows are formed when light is blocked by an object. Light reflects off surfaces at the same angle it hits them, following the law of reflection. White light is made up of the colors of the rainbow which can be split and recombined.
This document discusses how vision works and the science of reflection. It explains that light reflects off shiny, smooth surfaces like mirrors, while it scatters off rough surfaces. When light hits different materials, it may reflect, scatter, or refract. Reflection causes light to bounce back at the same angle, while refraction bends the light. Experiments are described to observe reflection using mirrors and the bending of light when it passes through water or other transparent materials.
This document discusses various sources of light and how light interacts with objects. It covers how light travels from sources to our eyes, how we see objects that are not light sources via light reflecting off of them, and how reflection works with both rough and shiny surfaces. It also explores color, how white light is composed of many colors, and how combining colors of light produces new colors.
The document discusses several key properties of light, including:
- Reflection - Light bounces off surfaces at the same angle it hits.
- Refraction - Light bends as it passes from one medium to another, changing speed. The degree of bending depends on the medium's index of refraction.
- Interference - When two light waves meet, they can constructively or destructively interfere based on how their crests and troughs align.
It explores light's dual nature as both a wave and particle, demonstrated through experiments like Young's double-slit experiment showing light's wave-like interference patterns, and the photoelectric effect showing its particulate properties.
1) Light travels in straight lines and is a form of energy that travels much faster than sound.
2) We see objects because they reflect light into our eyes, and shadows are formed when light is blocked.
3) Mirrors come in plane, convex, and concave shapes and can form real or virtual images depending on their shape and whether the light rays actually meet or appear to meet.
Light travels in straight lines and can be reflected or refracted. There are three types of materials: transparent, translucent, and opaque. Shadows are formed when an object blocks light. The length and shape of a shadow depends on the position of the light source and object. An experiment was conducted to determine which material - transparent plastic, tissue paper, or black paper - makes the darkest shadow. Black paper produced the darkest shadow because it is opaque and does not let any light pass through.
The document contains information about a student's foundation portfolio for media including a chosen brief to design the front cover and contents page of a school/college magazine. It includes sample front covers and contents pages of magazines following conventions such as mastheads, cover lines, and images. It also provides representations of celebrities on magazine covers analyzing aspects like costumes, poses, and expressions to engage readers. Ideas and plans are proposed for the student's own magazine cover and contents page design incorporating conventional elements.
Cinco estudiantes realizaron trabajos prácticos, exámenes y obtuvieron promedios. Tres estudiantes aprobaron con promedios entre 7.0 y 8.3, mientras que uno reprobó con 5.3 y otro suspendió con 4.7.
Student entrepreneurship
Acceleration through Smart Innovation
iMinds business acceleration
Smart Innovator
Internationalizing your business
Singapore
FIT support
Go West
El Panel de Control de Windows proporciona acceso a herramientas para configurar y personalizar el sistema operativo, así como mantener la seguridad y el rendimiento del dispositivo. Permite gestionar programas, hardware, conexiones de red e Internet, actualizaciones, copias de seguridad, y establecer opciones de energía, sonido, pantalla y más. Asimismo, ofrece funciones para crear cuentas de usuario y control parental.
The legend of Jesse James -THE AMERICAN ROBIN HOOD
Jesse James and the Widow
• One day, as Jesse James and his gang were riding through Missouri, they saw a farmhouse and stopped to ask for something to eat. A widow lived there with three small children. She didn't have much in the house, but shared with them what she had.
• It was while they were eating lunch that Jesse James noticed that something was bothering this generous widow. He questioned her about it, and she broke down and told him her story. The mortgage was due on the house that very day, and since her husband had died, she did not have the money to pay it. Her landlord was not a generous man, and was sure to put her children and herself out on the street.
• "How much money do you need to pay the mortgage?" Jesse asked the widow.
• "Fifteen hundred dollars," the widow sobbed.
• Jesse James took out his money bag, counted out $1500 dollars and presented it to the widow.
• "I can't take this," she protested, but Jesse James insisted she use the money to pay off the mortgage.
• "Just make sure you get a receipt," he warned her, and she promised that she would. Then he got a description of the man, and left with his gang.
• Jesse James and his gang waited in the woods near the house until the man had collected his money from the widow. Then they rode out onto the road and stole their money back from the landlord.
THE END
• WHAT DO YOU THINK ABOUT THIS STORY ?
• WAS JESSE JAMES AN OUTLAW OR A HERO?
• DO WE HAVE OUTLAWS OR HEROES LIKE THIS IN OUR COUNTRY?
• CAN YOU NAME THEM?
Simón espera a su madre Rita al final de su recorrido de senderismo de 3 meses y 92 días, a lo largo del cual Rita reflexiona sobre su pasado como alcohólica y mala madre. Al reencontrarse, Rita le asegura a Simón que ha cambiado y valorará cada momento con él.
Tuberculosis (TB) is caused by the Mycobacterium tuberculosis bacterium. When someone with TB coughs or sneezes, the bacteria are expelled into the air and can be inhaled by others. If breathed in, the bacteria initially infect the lungs. In the lungs, the bacteria can multiply and cause lesions and inflammation. Other types of microorganisms besides bacteria, such as viruses, can also cause infectious disease. When the body is exposed to TB bacteria, it mounts an immune response to fight the infection by using white blood cells, antibodies, and other mechanisms of defense.
Esta herramienta está especialmente indicada para profesionales de la educación dedicados al desarrollo y publicación de materiales de enseñanza y aprendizaje a través de la web, evitando que tengan que tener conocimientos previos de programación. Actualmente, gracias a nuevas herramientas tecnológicas, podemos usar internet como un instrumento más para la actividad académica, ofreciendo oportunidades para presentar contenidos e interactuar con ellos.
This document summarizes information about CERB JSC, an electrical repair company in Bulgaria, and the Bulgarian financial market. It provides background on CERB JSC, describing its history and operations. It analyzes CERB JSC's financial results, working capital, investment practices, and current funding. It also describes the Bulgarian financial market institutions and common funding practices in Bulgaria's electrical industry. Finally, it proposes plans for CERB JSC to improve its self-funding ability and access to external funding, such as optimizing its supply chain, receivables, and payables.
Noor Islam is seeking a position that allows him to utilize his electrical engineering experience and skills. He has a Bachelor's degree in Electrical Technology from UET Peshawar and over 10 years of experience in various electrical engineering roles, including as a site engineer, management category engineer, and technician. His experience includes electrical design, installation, maintenance, troubleshooting, and project management. He is proficient in AutoCAD, Microsoft Office, and computer hardware.
Este documento fornece informações sobre um curso de E-Commerce/Comércio Eletrônico ministrado por um professor com experiência acadêmica e profissional. O documento inclui o currículo do professor, o plano de aula, conceitos sobre E-Commerce e panoramas do mercado digital.
Sajikumar CV provides contact information and summarizes his 23+ years of experience in electrical engineering roles. He has worked on onshore and offshore oil and gas projects in several countries. His roles have included project engineering, site supervision, inspections, and commissioning. He is seeking a position where he can utilize his leadership skills and technical expertise to complete projects safely, efficiently and to high quality standards.
Este documento presenta información sobre el campo eléctrico. Define el campo eléctrico como un campo de fuerza creado por la atracción y repulsión de cargas eléctricas. Explica que el campo eléctrico tiene una dirección y magnitud en cualquier punto del espacio y se representa mediante líneas de campo. También analiza cómo varía el campo eléctrico dependiendo de si la carga es positiva o negativa.
Este documento resume las principales diferencias entre los sistemas operativos Windows 7, 8 y 10. Windows 7 presenta el menú de inicio tradicional con opciones de apagado y reinicio, mientras que Windows 8 elimina el menú de inicio en favor de una interfaz de estilo metro. Windows 10 reintroduce el menú de inicio con opciones adicionales y permite ejecutar múltiples aplicaciones simultáneamente. Otras diferencias clave incluyen que Cortana solo está disponible en Windows 10, Windows 8 introdujo un administrador de tareas renovado y Windows 10 tiene una
Como transformar dados de inventário em indicadores de perdas no varejoGunnebo Brasil
O documento discute como transformar dados de inventário em indicadores para redução de perdas. Ele explica que mapear as lojas com maiores perdas usando o gráfico de Pareto é um primeiro passo importante. Em seguida, recomenda-se gerenciar as informações por meio de indicadores em planilhas ou sistemas de BI para fornecer visibilidade sobre perdas por loja, departamento, categoria e outros níveis. Isso permitirá acompanhar o comportamento de perdas e aplicar estratégias mais assertivas.
DCCN 2016 - Protocols and technologies for IoTrudndccn
This document discusses emerging communication protocols and technologies for the Internet of Things domain. It begins with definitions of key IoT terminology and concepts. It then explains the different classifications of IoT including consumer IoT, industrial IoT, and their specific requirements. An overview of common IoT communication architectures and protocols is provided, such as MQTT, CoAP, ZigBee, Bluetooth LE, LoRaWAN and 3GPP NB-IoT. Examples of IoT applications like smart homes, smart factories, wearables and smart cities are described. The document concludes by envisioning the future of IoT and the technologies needed to realize its full potential.
1) El documento trata sobre el linfoma no Hodgkin, incluyendo su patogénesis, clasificaciones, manifestaciones clínicas, estudios para el diagnóstico y tratamientos.
2) Se describen diversos tipos de linfoma no Hodgkin como el linfoma folicular, linfoma difuso de células grandes y linfoma de Burkitt.
3) El tratamiento depende del tipo y estadio del linfoma, e incluye quimioterapia, radioterapia e inmunoterapia con anticuerpos monoclon
This document discusses light and how vision works. It explains that light must enter the eyes for us to see objects and that light can be emitted or reflected. It describes the laws of reflection, including that the angle of incidence equals the angle of reflection. The structure of the eye is also outlined, including the cornea, iris, pupil, lens, retina and blind spot. Proper care of the eyes is emphasized.
This document discusses light reflection and refraction. It explains that light reflects off objects, enabling us to see them, and transmits through transparent mediums. Spherical mirrors like those in spoons can form real or virtual images depending on the object position. Concave mirrors converge parallel rays to a focal point, allowing them to ignite objects, while convex mirrors diverge rays appearing to emanate from a focal point. The document explores image formation using spherical mirrors and defines terms like radius of curvature, focal length, and principal focus.
In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. ... Like all types of EM radiation, visible light propagates as waves. However, the energy imparted by the waves is absorbed at single locations the way particles are absorbed.
The document describes several experiments with mirrors, lenses, and prisms. It discusses how:
- Plane mirrors form erect, virtual images of the same size as the object.
- Concave mirrors can form real or virtual images, depending on the position of the object, and images formed can be smaller or larger than the object.
- Prisms disperse white light from the sun into the visible color spectrum due to refraction.
- Lenses also form real or virtual images, and convex lenses focus light to a point while concave lenses do not.
Light is a form of energy that allows us to see objects. Light may be emitted from luminous objects like the sun, or reflected off non-luminous objects. The human eye sees light when it enters the eye and forms an image on the retina, which sends signals to the brain. The iris controls the size of the pupil to regulate the amount of light entering the eye. Reflection of light follows two laws - the angle of incidence equals the angle of reflection, and the incident, normal and reflected rays lie in the same plane.
Light is an important source of energy that enables us to see. It travels extremely fast, at 300 million meters per second in a vacuum. When light hits surfaces, it can be reflected, refracted, or dispersed depending on the type of surface. Reflection occurs when light rays bounce off surfaces, while refraction is when light bends as it passes from one medium to another of different density. Dispersion is when white light separates into the colors of the visible spectrum through refraction in a prism.
Light is a form of energy that enables vision. Light travels in straight lines, and its direction can be changed via reflection or refraction. Reflection is the change in direction of light when it bounces off a surface like a mirror. The law of reflection states that the angle of incidence equals the angle of reflection. Reflection forms real or virtual images depending on whether light rays converge or appear to diverge. Spherical mirrors like concave and convex mirrors can form real or virtual images of different sizes and orientations. Lenses also refract light to form real or virtual images. Prisms disperse white light into visible colors via refraction.
This document provides an overview of light and optics topics including:
- Light travels in straight lines and can be reflected, absorbed, or pass through materials
- Shadows are formed when light is blocked and change size based on the position of the light source
- Refraction causes light to change direction when passing from one material to another, as seen through lenses and prisms
- Natural light sources like the sun can be investigated using shadows, while mirrors, lenses, and telescopes demonstrate optical principles.
Plane mirrors form virtual images that cannot be projected on a screen. Concave mirrors are used by dentists to magnify images of teeth and for applying makeup. Convex mirrors are installed at dangerous corners of roads and in supermarkets to prevent theft. When light hits mirrors, it follows the laws of reflection where the angle of incidence equals the angle of reflection and the incident ray, normal, and reflected ray are in the same plane. Refraction occurs when light passes from one medium to another of different density, causing it to change direction. This is why objects in water appear closer or bent. Prisms disperse white light into a rainbow spectrum due to differing refraction of colors. Scattering of light by particles in the
The Behavior of light on different substances Nikhil AV
This document discusses the behavior of light waves through reflection, refraction, diffraction, and transmission. It provides examples of how light interacts with different surfaces and materials. Light can be reflected off surfaces like mirrors. It is refracted as it passes from one medium to another, such as from air to water, causing objects to appear bent. Light diffracts when passing through narrow openings, forming interference patterns. Materials are classified as transparent, translucent, or opaque depending on how much light they allow to pass through.
The document discusses the refraction of light and how it causes optical illusions. It explains that when light travels from one material to another of different density, it changes direction. Specifically, light bends toward the normal when moving to a denser material, and away from the normal when moving to a less dense material. The document provides instructions for an experiment to observe and measure the refraction of light through a glass block at different angles of incidence.
This document provides an overview of light and how it behaves. It discusses key topics like:
1) Light sources can be luminous (emit their own light) like the sun, or non-luminous (do not emit light) like planets. Light travels in straight lines.
2) When light hits an object, it can be reflected, allowing us to see the object. Plane mirrors form images that are upright, the same size, and laterally inverted compared to the object.
3) A pinhole camera can be used to form small, inverted, and real images of outside objects by passing light through a small hole into a box. Natural pinhole cameras are formed when sunlight passes through gaps
The document is about light, shadows, and reflection. It defines luminous and non-luminous objects, and explains how we see objects via light reflecting off of them. It describes transparent, translucent, and opaque objects and how they interact with light. It defines shadows and discusses the properties of shadows, including how they are formed when light is blocked by an opaque object. It also discusses rectilinear propagation of light, pinhole cameras, plane mirrors, and the reflection of light. Some experiments are suggested to demonstrate these concepts.
Light prepared by Yasir Khan.
Topic covered :- reflection, laws of reflection, types of images, refraction, multiple images, kaleidoscope, dispersion of light, human eye, defects of vision, cataract, care for eye.
Thank you.
In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. ... Like all types of EM radiation, visible light propagates as waves. However, the energy imparted by the waves is absorbed at single locations the way particles are absorbed.
Optics is the study of light, including its interactions with mirrors, lenses and other objects. When light strikes an object it can be reflected, transmitted, scattered or absorbed. Mirrors come in three types - plane, concave and convex. Plane mirrors reflect light at the same angle it is received. Concave mirrors curve inward and can form real or virtual images, while convex mirrors curve outward and always form virtual images. Lenses also come in concave and convex forms, with convex lenses able to form real or virtual images depending on the object position. Optical instruments like telescopes, microscopes and cameras use lenses and mirrors to collect, focus and magnify light and images.
1. Light travels in straight lines and can be reflected or refracted. Reflection occurs when light bounces off a surface, while refraction is when light changes speed and direction when passing through different materials.
2. Mirrors come in different shapes that determine whether images are virtual or real, and lenses use refraction to bend light and form images. Concave lenses form virtual images while convex lenses form real images.
3. White light is composed of all visible wavelengths combined, and different materials reflect or absorb particular wavelengths, determining their perceived color. Color mixing with light follows the same principles as mixing with pigments. Filters can be used to selectively transmit or block certain wavelengths of light.
Explore the captivating world of light with Class 8 Science Light curriculum. Delve into the properties, reflection, and refraction of light, and discover its role in forming images, vision, and natural phenomena. From the laws governing reflection to the wonders of the human eye, Class 8 Science Light sheds light on the fascinating science behind illumination. Unravel the mysteries of light and its applications in our everyday lives with comprehensive study materials and engaging lessons.
For more information, visit-www.vavaclasses.com
Light enables us to see by allowing light rays from luminous objects like the sun to reflect off non-luminous objects into our eyes. Light travels in straight lines called rays. When light rays strike a surface, some of the rays are reflected. The angle of incidence, or the angle between the incident ray and a line perpendicular to the surface called the normal, is equal to the angle of reflection, or the angle between the reflected ray and the normal. Mirrors form virtual upright images that undergo lateral inversion and are the same distance from the mirror as the original object. Ray diagrams can be used to illustrate the reflection of light rays off a plane mirror into the eye.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
ANAMOLOUS SECONDARY GROWTH IN DICOT ROOTS.pptxRASHMI M G
Abnormal or anomalous secondary growth in plants. It defines secondary growth as an increase in plant girth due to vascular cambium or cork cambium. Anomalous secondary growth does not follow the normal pattern of a single vascular cambium producing xylem internally and phloem externally.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
2. When we are present in a dark room, we are
not able to see any object.
Whenever we look a playground at late night,
nothing is visible.
What are the reasons behind it?
Why can’t we see objects in dark places?
LET US FIND OUT.
3. Light usually refers to visible light, which is electromagnetic
radiation that is visible to the human eye and is responsible for the
sense of sight. Visible light is usually defined as having a wavelength in
the range of 400nanometres (nm), or 400×10−9 m, to 700 nanometers –
between the infrared, with longer wavelengths and the ultraviolet, with
shorter wavelengths.
The main source of light on Earth is the Sun. Sunlight provides the
energy that green plants use to create sugars mostly in the form of
starches, which release energy into the living things that digest them.
This process of photosynthesis provides virtually all the energy used by
living things. Historically, another important source of light for humans
has been fire, from ancient campfires to modern kerosene lamps. With
the invention of electricity, electric lighting has all but replaced firelight.
THE REASON BEHIND IT.
4. T H E A N G L E O F I N C I D E N C E ( D E N O T E D A S
( ∠ I ) ) A N D T H E A N G L E O F R E F L E C T I O N
( D E N O T E D A S ( ∠ R ) ) A R E A L W A Y S E Q U A L .
T H E I N C I D E N T R A Y , T H E R E F L E C T E D R A Y
A N D T H E N O R M A L A T T H E P O I N T O F
I N C I D E N C E A L L L I E O N T H E S A M E P L A N E .
LAWS OF REFLECTION
5. 1ST LAW
•Fix a white sheet of paper on a drawing board or a table.
•Take a comb and close all its openings except one in the middle.
You can use a strip of black paper for this purpose.
• Hold the comb perpendicular to the sheet of paper. Throw light
from a torch through the opening of the comb from one side (Fig.
below).
•With slight adjustment of the torch and the comb you will see a
ray of light along the paper on the other side of the comb.
•Keep the comb and the torch steady. Place a strip of plane mirror
in the path of the light ray (Fig. 16.1). What do you observe?
6. 2ND LAW
•Perform previous activity again. This time use a sheet of
stiff paper or a chart paper.
•Let the sheet project a little beyond the edge of the
Table(Fig. below).
•Cut the projecting portion of the sheet in the middle. Look
at the reflected ray. Make sure that the reflected ray extends
to the projected portion of the paper.
•Bend that part of the projected portion on which the
reflected ray falls. Can you still see the reflected ray?
• Bring the paper back to the original position. Can you see
the reflected ray again?
• This infers the second law of reflection as the reflected ray
does not fall on the bended part of paper.
7.
8. IMAGE FORMED BY A PLANE MIRROR
• A source of light O is placed in front of a plane mirror PQ. Two rays OA
and OC are incident on it (Fig. below).
• Draw normals to the surface of the mirror PQ, at the points A and C.
• Then draw the reflected rays at the
points A and C. Call the reflected
rays AB and CD, respectively.
• Extend them backwards. They meet. Mark this point as I. For a viewer’s
eye at E , do the reflected rays appear to come from the point I.
• Since the reflected rays do not actually meet at I, but only appear to do
so, we say that a virtual image of the point O is formed at I.
• Such an image cannot be obtained on a screen.
• In an image formed by a mirror the left
of the object appears on the right and the
right appears on the left. This is known
as lateral inversion.
9. Imagine that parallel rays are incident on an irregular surface as
shown in Fig. a. Remember that the laws of reflection are valid
at each point of the surface. Use these laws to construct
reflected rays at various points. Are they parallel to one
another? You will find that these rays are reflected in different
directions. (Fig. b)
(b)(a)
10. When all the parallel rays reflected from a plane surface
are not parallel, the reflection is known as diffused or
irregular reflection. Remember that the diffused
reflection is not due to the
failure of the laws of reflection. It is caused by the
irregularities in the reflecting surface, like that of a
cardboard.
On the other hand reflection from a smooth surface like
that of a mirror is called regular reflection.
Images are formed by regular reflection.
11. Nearly everything you see around is seen due
to reflected light. Moon, for example, receives
light from the sun and reflects it. That’s how we
see the moon.
The objects which shine in the light of other
objects are called illuminated objects.
There are other objects, which give their own
light, such as the sun, fire, flame of a candle
and an electric lamp. Their light falls on our
eyes. That is how we see them.
The objects which emit their own light are
known as luminous objects.
12. REFLECTED LIGHT CAN BE
REFLECTED AGAIN
Recall the last time you visited a hair dresser.
He makes you sit in front of a mirror. After your
hair cut is complete, he places a mirror at your
back to show you how the hair has been cut.
Can you think how you could see the hair at the
back of your head? This marks the way of
showing of images through a periscope.
The periscope makes use of two plane mirrors.
Periscopes are used in submarines, tanks and
also by soldiers in bunkers to see things
outside.
13. Multiple Images
You are aware that a plane mirror forms
only a single image of an object. What
happens if two plane mirrors in
combination are used? Let us see.
14. Activity to show multiple images
formed by a plane mirror
• Take two plane mirrors.
• Set them at right angles to each other with their
edges touching (Fig. below).
• To hinge them you can use adhesive tape. Place a
coin in between the mirrors. How many images
of the coin do you see
(Fig. below)?
15. • Now hinge the mirrors using the adhesive tape at
different angles, say
45º, 60º, 120º, 180º etc.
• Place some object (say a candle) in between them.
Note down the number of images of the object in each
case.
• Finally, set the two mirrors parallel to each other.
Find out how many images of a candle placed between
them are formed (Fig. below).
16. Conclusion
Can you now explain how you can
see the back of your head at the hair
dresser’s shop?
This idea of number of images formed
by mirrors placed at an angle to one
another is used in a kaleidoscope to
make numerous beautiful patterns. You
can also make a kaleidoscope yourself.
17. Making of kaleidoscope
• To make a kaleidoscope, get three rectangular mirror strips about
15cm long and 4 cm wide each.
• Join them together to form a prism as shown in Fig.(a).
• Fix them in a circular cardboard tube or tube of a thick chart paper.
Make sure that the tube is slightly longer than the mirror strips.
• Close one end of the tube by a cardboard disc having a hole in the
centre, through which you can see [Fig.(b)].
• To make the disc durable, paste a piece of transparent plastic sheet
under the cardboard disc. At the other end, touching the mirrors, fix
a circular plane glass plate [Fig. 16.12(c)].
• Place on this glass plate several small pieces of coloured glass
(broken pieces of coloured bangles).
• Close this end of the tube by a ground glass
plate.
• Allow enough space for the colour pieces
to move around.
18. Introduction to Kaleidoscope
Your kaleidoscope is ready.When you peep
through the hole, you will be able to see a
variety of patterns in the tube.
Interesting feature of a kaleidoscope is
that you will never see the same pattern
again. Designers of wallpapers and fabrics
and artists use kaleidoscopes to get ideas for
new patterns.To make your toy attractive,
you can wrap the kaleidoscope in a coloured
paper.
19. Sunlight — White or
Coloured
In ClassVII, we learnt that the sunlight is
referred to as white light.We also learnt that
it consists of seven colours.
Here is another activity (next Activity)
showing that sunlight consists of several
colours.
20. Dispersion of light
Get a plane mirror of suitable size.
Place it in a bowl (Katori) as shown in Fig. (a).
Fill the bowl with water.
Put this arrangement near a window such that direct sunlight falls on the mirror.
Adjust the position of the bowl such that the reflected light from the mirror falls
on a wall. If the wall is not white, fix a sheet of white paper on it.
Reflected light will be seen to have many colours. How can you explain this?
The mirror and water form a prism.This breaks up the light into its colours, as we
learnt in ClassVII.
Splitting of light into its colours is known as dispersion of light. Rainbow is a
natural phenomenon showing dispersion.
(a)(b)
21. We see things only when light coming from them enters our eyes.
Eye is one of our most important sense organs. It is, therefore,
important to understand its structure and working.
The eye has a roughly spherical shape. Outer coat of the eye is
white. It is tough so that it can protect the interior of the eye
from accidents. Its transparent front part is called cornea. (Fig.
below). Behind the cornea, we find a dark muscular structure
called iris. In the iris, there is a small opening called the pupil.
The size of the pupil is controlled by the iris. The iris is the part
of that eye which gives it its distinctive colour. When we say that
a person has green eyes, we refer actually to the colour of the
iris. The iris controls the amount of light entering into the eye.
Let us see how.
22. Look into your friend’s eye. Observe the size
of the pupil.
Throw light on her eye with a torch. Observe
the pupil now.
Switch off the torch, and observe her pupil
once again. Do you notice any change in the
size of the pupil?
In which case was the pupil larger? Why do
you think it was so?
In which case do you need to allow more
light in the eye, when the light is dim or
bright?
23. Behind the pupil of the eye is a lens which is
thicker in the centre. What kind of lens is
thicker at the centre?
Recall what you learnt about lenses in Class
VII. The lens focuses light on the back of the
eye, on a layer called retina(Fig. 16.14).
Retina contains several nerve cells.
Sensations felt by the nerve cells are then
transmitted to the brain through the optic
nerve.
There are two kinds of cells
(i) cones, which are sensitive to bright
light and
(ii) rods, which are sensitive to dim light.
Besides, cones sense colour. At the junction
of the optic nerve and the retina, there are
no sensory cells, so no vision is possible at
that spot. This is called the blind spot. Its
existence can be demonstrated by the
following activity:
24. Activity
Make a round mark and a cross on a sheet of paper with the spot to
the right of the cross (Fig. below). The distance between two marks
may be 6-8 cm. Hold the sheet of paper at arms length from the eye.
Close your left eye. Look continuously at the cross. Move the sheet
slowly towards you, keeping your eye on the cross. What do you
find? Does the round mark disappear at some point? Now close your
right eye. Look at the round mark now and repeat the activity. Does
the cross disappear? The disappearance of the cross or the round
mark shows that there is a point on the retina which
cannot send messages to the brain when light falls on it.
25. The impression of an image does not vanish immediately from the
retina. It persists there for about 1/16th of a second. So, if still images
of a moving object are flashed on the eye at a rate faster than 16 per
second, then the eye perceives this object as moving.
Perform the following activity to understand the concept.
Get a square piece of cardboard of side 6-8 cm. Make two holes as
shown in Fig. below. Thread a string through the two holes.
Draw/paste a cage on one side of the cardboard and a bird on the
other side. Twist the string and make the card twirl rapidly. Do you see
the bird in the cage?
The movies that we see are
actually a number of separate
pictures in proper sequence. They
are made to move across the eye
usually at the rate of 24 pictures
per second (faster than 16 per
second). So, we see a moving
picture.
26. Important Facts
Nature has provided eyes with eyelids to protect from any
object entering the eye. Eyelids also shut out light when not
required.
Eye is such a wonderful instrument that it (normal) can see
distant objects as well near objects clearly. The minimum
distance at which the eye can see objects distinctly varies
with age. The most comfortable distance at which one can
read with a normal eye is about 25 cm.
Some persons can see near objects clearly but cannot see
distant objects so clearly. On the other hand, some
persons cannot see near objects clearly but they can see
distant objects quite well. With suitable corrective lenses,
these defects of the eye can be corrected.
Sometimes, particularly in old age, eyesight becomes
foggy. It is due to the eye lens becoming cloudy. When it
happens, persons are said to have cataract. There is a loss of
vision, sometimes extremely severe. It is possible to treat
this defect. The opaque
lens is removed and a new artificial lens is inserted. Modern
technology has made this procedure simpler
and safer.
27. Care of the Eyes
It is necessary that you take proper care of your eyes. If there is any problem you should
go to an eye specialist. Have a regular checkup.
If advised, use suitable spectacles.
Too little or too much light is bad for eyes. Insufficient light causes eyestrain and
headaches. Too much light, like that of the sun, a powerful lamp or a laser torch can
injure the retina.
Do not look at the sun or a powerful light directly.
Never rub your eyes. If particles of dust go into your eyes, wash your eyes with clean
water. If there is no improvement go to a doctor.
Wash your eyes frequently with clean water.
Always read at the normal distance for vision. Do not read by bringing your book too
close to your eyes or keeping it too far.
One should include in the diet components which have vitamin A. Raw carrots, broccoli
and green vegetables (such as spinach) and cod liver oil are rich in vitamin A. Eggs, milk,
curd, cheese, butter and fruits such as papaya and mango are also rich in vitamin A.
28. Animals have eyes shaped in different ways. Eyes of a crab are quite small but
they enable the crab to look all around. So, the crab can sense even if the enemy
approaches from behind. Butterfly has large eyes that seem to be made up of
thousands of little eyes (Fig. below). It can see not only in the
front and the sides but the back
as well.
A night bird (owl) can see very well
in the night but not during the
day. On the other hand, day light
birds (kite, eagle) can see well
during the day but not in the
night. The Owl has a large cornea
and a large pupil to allow more
light in its eye. Also, it has on its
retina a large number of rods and
only a few cones. The day birds
on the other hand, have more
cones and fewer rods.
29. Some persons, including children, can be visually handicapped. They have very limited vision to
see things. Some persons cannot see at all since birth. Some persons may lose their eyesight
because of a disease. Such persons try to identify things by touching and listening to voices
more carefully. They develop their other senses more sharply. However, additional resources can
enable them to develop their capabilities further.
Resources can be of two types : Non-optical aids and optical aids.
Non-optical aids include visual aids, tactual aids (using the sense of touch), auditory aids (using
the sense of hearing) and electronic aids. Visual aids, can magnify words, can provide suitable
intensity of light and material at proper distances. Tactual aids, including Braille writer slate and
stylus, help the visually challenged persons in taking notes, reading and writing. Auditory aids
include cassettes, tape recorders, talking books and other such devices. Electronic aids, such as
talking calculators, are also available for performing many computational tasks. Closed circuit
television, also an electronic aid, enlarges printed material with suitable contrast and
illumination. Nowadays, use of audio CDs and voice boxes with computers are also very helpful
for listening to and writing the desired text.
Optical aids include bifocal lenses, contact lenses, tinted lenses, magnifiers and telescopic aids.
While the lens combinations are used to rectify visual limitations, telescopic aids are available to
view chalkboard and class demonstrations.
30. The most popular resource for visually challenged persons is
known as Braille.
Louis Braille, himself a visually challenged person, developed
a system for visually challenged persons and published it in
1821.
Braille system has 63 dot patterns or characters. Each
character represents a letter, a combination of letters, a
common word or a grammatical sign. Dots are arranged in
cells of two vertical rows of three dots each.
The present system was adopted in 1932. There is Braille
code for common languages, mathematics and scientific
notation. Many Indian languages can be read using the
Braille system. Patterns of dots to represent some English
alphabets and some common words are shown below.
These patterns when embossed on
Braille sheets help visually
challenged to recognize words by
touching. To make them easier to
touch, the dots are raised slightly.
31. Visually challenged people learn the Braille system by beginning with
letters, then special characters and letter combinations. Methods depend
upon recognition by touching. Each character has to be memorized. Braille
texts can be produced by hand or by machine. Type writer - like devices and
printing machines have now been developed.
Some visually challenged Indians have great achievements to their
credit. Diwakar, a child prodigy has given amazing performances
as a singer.
Mr. Ravindra Jain, born completely visually challenged,
obtained his Sangeet Prabhakar degree from Allahabad.
He has shown his excellence as a lyricist, singer and
music composer.
Mr. Lal Advani, himself visually challenged, established
an Association for special education and rehabilitation
of disabled in India. Besides, he represented India on
Braille problems to UNESCO.
Helen A Keller, an American author and lecturer, is
perhaps the most well-known and inspiring visually
challenged person. She lost her sight when she was
only 18 months old. But because of her resolve and
courage she could complete her graduation from a
university. She wrote a number of books including
The Story of my Life (1903).