Unit 30 Light and the Electromagnetic Spectrum part 1

Science Interactive LTD Multimedia CD-ROM for PC is a collection of 38 units totalling over 1150 PowerPoint slides matched to current single and double Science GCSE syllabuses. Each unit covers a wide range of different delivery and learning styles, offering an exciting way to involve your pupils during lessons or revision sessions. All styles of teaching and learning are supported through use of high quality images, graphics, challenging exercises and questions. Units can be used in the classroom via an interactive whiteboard , data projector or used during individual study via a PC or school network. Full users’ licence is available under our ‘ comprehensive package ’ or lessons can be purchased separately. Science Interactive LTD. PO BOX 50764 LONDON NW6 9AT email: sales@science-interactive.co.uk web: www:science-interactive.co.uk GCSE SCIENCE OCR EDEXCEL AQA Science Interactive LTD Copyright 2005 Unit 19: The Transitional Metals Unit 18: Metals and their Properties Unit 17: The Alkali Metals Unit 16: The Periodic Table and its Elements Unit 15: Genetic Engineering Unit 14: Evolution and Human Impact Unit 13: Inheritance and Selection Unit 12: Mitosis and Meiosis Unit 11: Flow of Energy and Elements through the Environment Unit 10: Water Transport in Plants Unit 9: Photosynthesis in Green Plants Unit 8: Drugs and Bad Body Maintenance Unit 7: Hormones and the Endocrine System Unit 6: Human Homeostasis Unit 5: Nervous System and the Senses Unit 4: The Respiratory System Unit 3: Healthy Body and Immunity Unit 2: The Circulatory System Unit 1: The Digestive System Unit 38: Cells, Tissue, Organs and Organs systems Unit 37: Natural Forces Unit 36: Sound and Hearing Unit 35: The Alkaline Earth Metals Unit 34: The Earth and Plate Tectonics Unit 33: Earth and Space Unit 32: Newton's Forces and the Effects of Forces Unit 31: Radioactivity Unit 30: Light and the Electromagnetic Spectrum Unit 29: Electricity Unit 28: Generating Electricity and its Domestic Use Unit 27: Energy Unit 26: Rates of Reaction Unit 25: The Noble Gases, their Properties and Uses Unit 24: The Halogens, their Uses and Compounds Unit 23: Ionic and Covalent Compounds Unit 22: Elements, Molecules and Compounds Unit 21: Rock Cycle Unit 20: Crude Oil and its Products

Unit 30

Light and the Electromagnetic Spectrum

Science Interactive LTD Copyright 2005 (LW) (MW) (VHF) radio waves (UHF) microwaves Infra red light Ultra - Violet X - rays Gamma 10 3 m 10 2 m 10 1 m 1m 10 - 1 m 10 - 2 m 10 - 4 m 10 - 6 m 10 - 8 m 10 - 10 m 10 - 12 m

That visible light is just a small part of the much larger electromagnetic spectrum.

That the electromagnetic spectrum is a collection of waves with similar properties.

That these waves have different uses based on their individual properties.

That the speed of light can be calculated using Michelson’s experiment.

That visible white light is a collection of the seven colours of the spectrum.

That visible light can either be reflected or refracted.

Some of the examples of devices that rely on reflection or refraction of visible light.

That visible light can be totally internally reflected, for example in optic fibres.

The similarities between the human eye and a camera.

How the human eye forms an image.

Electromagnetic, Spectrum, Radio waves, Ultrasound, Microwaves, Infra red, Visible, Light, Ultraviolet, X rays, Gamma rays, Radiation, Speed, Reflection, Refraction, Wavelength, Rainbow, Eye, Lens, Retina, Cornea, Optic & Image. Unit 30: Light and the Electromagnetic Spectrum web: www.science-interactive.co.uk email: sales@science-interactive.co.uk Science Interactive LTD PO BOX 50764 LONDON NW6 9AT Click mouse to begin Science Interactive LTD Copyright 2005 Understand: Keywords:

Waves and their properties one Sound or light waves can be reflected, refracted and diffracted. The wavelength is the distance between two successive compressions (crest or troughs) The f ____________ measured in hertz (cycles per second) is the number of complete vibrations in each second. The amplitude is the average height of a crest or trough from the midpoint or the undisturbed position. The size of the amplitude determines the v_________ of the sound. The wavelength or frequency determines the pitch of the sound. Wavelength and amplitude: Science Interactive LTD Copyright 2005 Word bank: frequency volume Amplitude midpoint Wavelength Velocity of wave Crest Trough From a single point source, waves like ripples on a pond spread out in all directions. The distance between two successive compressions is known as the wavelength. The amplitude is the average height of a crest or a trough from the midpoint. What happens to the volume and pitch of a sound, if you alter the amplitude and wavelength ?

Wavelength (cm)

Amplitude (cm)

Frequency (Hz)

Notes Diagram Wavelength & amplitude Waves from a single point source Waves

Waves and their properties two There are two types of w_______, longitudinal and transverse waves. Longitudinal: These waves travel from the source in waves of compression, parallel to the direction of the moving wave. Sound waves are longitudinal waves. Transverse: These waves travels from the source at right angles to the direction of the wave. Light waves are transverse waves. Types of waves: Science Interactive LTD Copyright 2005 Word bank: waves frequency Direction of wave Direction of wave Transverse: The wave travels from the source at right angles to the direction of the wave. Longitudinal: These waves travel from the source in waves of compression parallel to the direction of the moving wave. Remember: The pitch of a sound is determined by the wave’s frequency and is measured in hertz. The volume level in decibels is determined by the wave’s amplitude.

Wavelength (cm)

Amplitude (cm)

Frequency (Hz)

Diagram Longitudinal ...Sound Transverse ...Light Waves

Analogue or digital We now live in a digital age, for example digital r_____ and TV... but what does this all mean ? Analogue waves carry information from a transmitter in smooth varying waves, that can have a changing wavelength and amplitude. Analogue waves can be subject to interference and corruption. In digital systems, for example digital radio , the analogue carrier wave is converted to definite values usually on or off or 1’s and 0’s. Digital signals are less affected by interference from other sources. Digitally stored data like mp 3 files are reconstructed into their original analogue sound waves during their play through a sound system. Analogue or digital: Science Interactive LTD Copyright 2005 Word bank: radio Direction of wave Direction of wave 01 011 0101 0111 01001 01011 011111 0111111 01111101 011111011 Digital code Recorded, transmitted and stored music, for example mp 3 files are stored as a series of numerical values (1’s and 0’s) rather than fluctuations in wavelength and amplitude of analogue sound. Over the last decade, digital medium (music radio, television and photography) has replaced its older counterparts. Radio, television and broadband now all rely on digital systems to transfer all types of information, error free. Diagram Digital Analogue Digital media

The electromagnetic spectrum Visible light is only a very small fraction of a much larger spectrum containing many other waves with their own individual properties. These family of waves, unlike visible light cannot be seen with the human eye. Their properties change according to their w___________. These family of waves do share some properties, for example, they all travel at the same s_______ through a vacuum and are able to transfer energy. Give one use for each of the waves listed below ? The electromagnetic spectrum: 10 3 m 10 2 m 10 1 m 1m 10 -1 m 10 -2 m 10 -4 m 10 -6 m 10 -8 m 10 -10 m 10 -12 m (LW) (MW) (VHF) radio waves (UHF) microwaves Infra red light Ultra-Violet X-rays Gamma Science Interactive LTD Copyright 2005 Word bank: wavelength speed Picture Pinhead Cell Insect Human Molecule Atom Stonehenge Buildings Relative size Wave Wavelength (m)

Sources and detecting electromagnetic waves The Sun gives out all the wave forms of the e.m spectrum however, only a small percentage including visible l_______ reaches the Earth’s surface. This is because our atmosphere stops many of the harmful waves reaching us. Visible light can be detected by the human e_____. Skin can also detect infra red waves as heat. In order to detect other waves forms like infra red radio waves, we need to use a device or detector. Sources and detection of electromagnetic waves: 10 3 m 10 2 m 10 1 m 1m 10 -1 m 10 -2 m 10 -4 m 10 -6 m 10 -8 m 10 -10 m 10 -12 m radio waves microwaves Infra red light Ultra-violet X-rays Gamma Science Interactive LTD Copyright 2005 Word bank: light eye Detectors Radioactive substances X ray tubes Sun Mercury lamps Sun Hot objects Hot objects Sun Ovens Radar Transmitters Sources Ultraviolet X rays Light Infra red Gamma Microwaves Radio Wave Wave Wavelength (m)

Properties of all electromagnetic waves Electromagnetic waves consist of oscillating electric and magnetic fields, which all travel at the speed of light. The spectrum of electromagnetic waves ranges from very long wavelengths, for example r________ waves to very short wavelengths like g______ and x-rays. All these types of radiation are produced by excited atoms and their sub atomic particles (Neutron, Protons and Electrons) and during nuclear fission. Give two uses for gamma rays and radio waves ? Properties of all electromagnetic waves: Science Interactive LTD Copyright 2005 Word bank: radio gamma All electromagnetic waves, like visible light can be reflected by smooth, hard surfaces like a mirror. The angle of incidence is equal to the angle of reflection. Reflection All electromagnetic waves like light can be bent, when they travel through transparent materials like glass and water. This is called refraction. Refraction All electromagnetic waves are able to transfer energy from one place to another. Infra red rays transfer, for example heat energy. All electromagnetic waves travel at a speed of 300,000 kms -1 through a vacuum. Nothing in the known universe travels faster than light or other e.m waves. Notes Diagram Speed Energy transfer

The electromagnetic spectrum one Radio waves are a family of waves, with relatively long wavelengths. Medium and long wave radio are used to transmit signals over long d_________, because they are reflected around the curve of the Earth’s atmosphere. Microwaves have the shortest wavelength of radio waves and are used to h______ food in ovens as well as image planes. This is known as radar. Infra red, the next wave type, is given out by every warm object. Using infra red cameras, a thermograph can tell us the temperature of an object. The electromagnetic spectrum: (LW) (MW) (VHF) radio waves (UHF) microwaves Infra red 10 3 m 10 2 m 10 1 m 1m 10 -1 m 10 -2 m 10 -4 m 10 -6 m Science Interactive LTD Copyright 2005 Word bank: distances heat Infra red rays are given off by all warm objects. You cannot see these rays but your skin can sense them. Above, a thermograph of a small infant. Microwave ovens and mobile phones use microwaves. In micro-waves, energy is transferred from the waves to the food. Radar uses microwaves, to obtain information on the position of planes in the sky. These waves are bounced back and collected by radar dish. Radio signals carry sound information and can travel many kilometres through the Earth’s atmosphere and ionosphere. Notes Diagram Infra red Microwaves Radar Radio waves Wave Diagram Wavelength (m)

The electromagnetic spectrum two Visible light is only a very small fraction of a much larger spectrum called the electromagnetic s_________ which contains many other wavelengths. Light is released from various sources including the Sun and hot objects like a b_____ filament. Visible light has wavelengths between 750 and 400 nanometres. The wavelength in nanometres, determines the colour of light, for example longer wavelengths (750nm) are red in colour and shorter wavelengths ( 400nm ) are violet in colour. What wavelength in nanometres is infra red ? The electromagnetic spectrum: light 10 -6 m 10 -7 m Science Interactive LTD Copyright 2005 Word bank: spectrum bulb Pulses of light can carry information. Broadband internet currently uses optic cables to carry large amounts of information. White light can be separated into its 7 spectrum colours: This can be done by a glass prism or rain drops (ROYGBIV) The human eye has evolved to make use of only a very small fraction of the e.m. spectrum. It can detect all seven colours. The Sun, light bulbs and hot objects all emit visible light. They travel in a straight lines through a vacuum at a speed of 300,000 kms -1 . Notes Diagram Communicating Separating light Human eye Visible light Wave Diagram Wavelength (m)

The electromagnetic spectrum three Waves with shorter wavelengths including, UV rays, X-rays and Gamma rays have a higher penetrating ability . X-rays, produced by an X-ray tube penetrate soft tissue. They are used to image broken b_______. Gamma-rays, with the shortest wavelength can penetrate even concrete and lead. Gamma rays carry high amounts of e________ and are very dangerous. They are used to sterilise food and medical instruments. The electromagnetic spectrum: 10 -8 m 10 -10 m 10 -12 m Ultra-violet X-rays Gamma Science Interactive LTD Copyright 2005 Word bank: bones energy Gamma rays penetrate thick concrete and lead. They are used to sterilise foods, killing all bacteria present on the food’s surface. X-Rays can penetrate soft tissue but not hard bone. These rays are used to image broken bones. Long term exposure can cause cancer. UV rays produced by the Sun can penetrate and damage skin cells causing skin cancer. Pictured above is a sun bed using UVB rays for a suntan. Notes Diagram Gamma rays X-Rays UV Light Wave Diagram Wavelength (m)

Visible light Our eyes are only sensitive to visible light. The light we see has a wavelength range of between 750 to 400 nanometres (1000 nanometres = 0.001 millimetre.) White light is a mixture of s_______ colours. White light can be split by a glass p______. This is because when light travels through glass, different colours all slow down, but by different amounts depending on their wavelength. Red light ( longer wavelengths ) is slowed the least and so is refracted through the smallest angle. Violet light ( shorter wavelengths ) is slowed down the most and so is refracted through the largest angle. Spectrum of white light: Science Interactive LTD Copyright 2005 Word bank: seven prism 750nm 600nm 500nm 400nm Infra red ultra violet Red Orange Yellow Green Blue Indigo Violet White light from a single source can be split using a glass prism. Violet is deviated the most because it has the shortest wavelength. Red light with the longer wavelength is deviated the least. Splitting light The spectrum of colours and their wavelengths. The human eye is sensitive to red, green and blue light only. Much like a television, your brain uses these primary colours to form all other colours. Visible wavelengths Nature’s way of splitting white light. Each raindrop acts like a mini-prism. Here red light is bent the least and violet light is bent the most. The Sun is the primary source of white light, and all the colours of the spectrum. It supplies the Earth with all the light and heat energy that we require. Sun Rainbow

Calculating the speed of light A scientist called Albert Michelson used an octagonal mirror to measure the speed of light . He shone a single ray of light onto the octagonal mirror, which was then reflected back to a mirror on a distant mountain 36 km away. A m_______ on that mountain reflected the light ray back along the same path to the same mirror on the octagon. In one experiment, the octagonal mirror rotated sufficiently fast, so that the light coming back from the mountain hit mirror B. Mirror B had moved into the same place as mirror A was when the light ray left it. Calculating the speed of light: Distance between source and mirror 36 km Source A B Mirror Science Interactive LTD Copyright 2005 Word bank: mirror (5) How far did the light travel in metres (72 km) ? (6) Use your answers for a and b to calculate the speed of light (ms -1 ) ? (3) How long (in seconds) did the octagonal mirror take to make one complete revolution ? (4) How long did it take the octagon to turn so that mirror B was in the same position as mirror A ? (2) The octagonal mirror rotated at 31250 r.p.m . How many revolutions in one second did the octagonal mirror make ? 1: How many degrees ( o ) would the octagon turn through so that mirror B is in exactly in the same place as mirror A ? Show your working out. Total distance travelled Speed of light Calculation Experiment Revolution rate Time elapsed for

Colour and light When white light ( red orange yellow green blue indigo violet ) illuminates a green object, it absorbs red, orange, yellow, blue, indigo & violet wavelengths , only leaving green light to be reflected into your eye. This is how the human e____ perceives colours. Colours used in paints and clothing work by absorbing most of the different c o l o u r s in the spectrum, r___________ only the colour it appears. How does a glass prism separate the seven colours of the spectrum ? Coloured objects: Red Blue Black Yellow Object colour Colours absorbed Colours reflected Red O Y G B I V Red Blue ___________ ? _______ ? Black ___________ ? _______ ? Yellow ___________ ? _______ ? Science Interactive LTD Copyright 2005 Word bank: eye reflecting Solving colours Materials like cloth and plastic are dyed using chemicals designed to reflect only certain colours from the colour spectrum. White light from the Sun or a filament bulb is a mixture of the seven colours of the spectrum: red orange yellow green blue indigo violet. Notes Diagram Mixing colour Colours

Addition of colour Adding the three primary colours: red , green and blue gives white light. In your eyes, on the surface of the retina, your cone cells are sensitive to these three primary colours. Adding two p_________ colours results in a secondary colour. There are three secondary colours: yellow , a purple like colour called magenta , and a greeny-blue colour called cyan . A television set uses all three primary colours (red, green & blue) to form a complete i________ showing a full range of colours. Adding colours: Science Interactive LTD Copyright 2005 Word bank: primary image A television uses only the primary colours, red, green and blue to form a coloured image. The amount of primary light is controlled by a chip to give the right image. The three primary colours red , green and blue form white light in the centre as a result of mixing all three. The secondary colours ( magenta , cyan & yellow ) result when only two primary colours are mixed. Notes Diagram Mixing primary colours Television

Reflection of light one Visible light travels in straight lines, unless it meets an object for example a mirror or a glass block. Reflection is the rebounding of l_____ from a smooth, shiny surface. Smooth surfaces such as clean glass, reflects light back to the observer in parallel rays. This is called regular reflection, where the angle of incidence is equal to the angle of reflection . Surfaces which are not smooth, for example the uneven surface of a road, diffuses light in all directions. This is called diffuse reflection. Understanding reflection: Science Interactive LTD Copyright 2005 Word bank: light Object Actual path of light Plane mirror Imagined path of light The image looks as if it is here The image appears to the observer as far away from the plane mirror as the true object is in front. The above diagram shows how the reflected rays from a plane mirror forms a virtual image. Notice that the angle of incidence is equal to the angle of reflection (Example, both are 45 o ) Light is reflected by smooth, shiny materials like metals and glass. Rough surfaces are poor reflectors of light. Light can also dispersed in all directions by rough surfaces or even fog. Notes Reflection from a plane mirror Diagram Regular reflection Diffuse reflection

Reflection of light two We can use different mirrors to reflect light in many ways. There are two kinds of mirrors; concave and c_________ mirrors. Concave mirrors converge parallel rays of light forming a focal point. For a near object, a concave mirror produces a magnified image. Convex mirrors s_________ or diverge parallel rays of light away from the imaginary focal point. The image in a convex mirror is always reduced in size giving a very wide field of view. Name three devices that use convex or concave mirrors ? Mirrors and their uses: Science Interactive LTD Copyright 2005 Word bank: convex spread Shop mirrors use a convex mirror which produces a wide field of view. Why are these types of mirrors used in shops. A torch uses a concave mirror to produce a beam of light from a single point source or bulb. What is the mirror made from ? A concave mirror is a converging mirror. The image produced by a concave mirror, is virtual, always smaller and the upside down. A convex mirror is a diverging mirror. The image produced by a convex mirror, is virtual, always larger and the right way up. Notes Torch Shop security Diagram Convex mirror Concave mirror

Image Object Object Image Convex mirror Concave mirror Reflection of light three We can use different mirrors to reflect light in many ways. There are two kinds of mirrors; concave and convex mirrors . Concave mirrors converge p________ rays of light forming a focal point. A concave mirror can be used to focus the Sun’s rays to collect light energy. They can also be used to collect sound radar, and television signals. Sky television require the installation of a satellite dish, which is c_________ in shape, attached to an outer wall. This dish will collect and focus signals from a satellite in a geostationary orbit. Describe how a solar cooker works using a concave mirror ? Mirrors and their uses: Science Interactive LTD Copyright 2005 Word bank: parallel concave Both convex and concave mirrors alter the way we see an image of an object. This is because, unlike plane mirrors their surface changes, therefore altering the way we see the image. Notes Concave mirror Diagram Convex mirror

Using mirrors and reflected light one The viewing periscope uses a simple arrangement of plane mirrors both placed at 45 o to the viewing object. Periscopes are found in s___________ to view their targets, perhaps an aircraft carrier or frigate. You can also use a periscope to view a pop band over a crowd. Design with the use of mirrors a device that can check for bombs or other objects that might be attached to the underneath part of cars...show your design with a diagram...remember to use your ruler when drawing light rays ! Mirrors and the periscope: Object Image Science Interactive LTD Copyright 2005 Word bank: submarines The periscope allows you to observe what is happening on the sea’s surface, when you are in a submarine. The target is a frigate ship. Rays from the object are reflected by plane mirrors both set at 45 o in the periscope. The image is virtual, smaller but the right way up ! Notes Image Diagram Inside a periscope Periscope

Using mirrors and reflected light two The reflecting telescope designed by Isaac Newton has a large concave mirror to collect reflected light from a d________ object like a planet in our solar system. The concave mirror also converges the light to a small plane mirror for the observers e_____. The eye lens acts like a magnifying glass to increase the size of the virtual image . Why should you never observe the sun using a pair of binoculars or a telescope...How can you safely observe the Sun during a solar eclipse ? Mirrors and the Newton telescope: Science Interactive LTD Copyright 2005 Word bank: distant eye An image of Saturn’s rings obtained using a Newton telescope. Telescopes like this one can be bought relatively cheaply. Best used away from major cities and light pollution. Reflected light from a distant object like a planet enters the telescope. It is reflected using a concave mirror and then enlarged through an eye lens. Notes Image Diagram Newton’s telescope Telescope

Refraction of light one Refraction is the bending of light waves when they pass from one medium (e.g. air) to another (e.g. glass.) If the s_______ of light is different in the two media, then light bends from its original path. The amount of bending depends on the material, the wavelength and the angle of entry. When light is slowed down, it will bend towards the normal, when light speeds up it bends a______ from the normal. This is the law of refraction. Refraction of light: Science Interactive LTD Copyright 2005 Word bank: speed away Example one: The spoon in this picture appears broken or interrupted. Example two: Light travelling through air, then water and glass is refracted because it is changing speed. Example three: The effect of refraction in this picture is to magnify the writing. Example four: A prism is able to separate white light into its separate colours, using refraction. Notes Example three Example four Diagram Example one Example two

1: Define the following terms: Electromagnetic spectrum, Radio waves, Ultrasound, Microwaves, Infra red, Visible light, Reflection, Refraction, Wavelength, Total internal reflection. 2: Look at the three diagram. Complete the table. 3: Answer the following: b) Give the full order of the electromagnetic spectrum starting with Gamma rays. Illustrate your answers with a diagram. Also give three properties of all electromagnetic waves. c) Give two examples of waves of the electromagnetic spectrum that can carry information. d) How do optic fibres carry information and explain total internal refraction. Use a diagram. e) Give one use for UV light and X-rays. Illustrate your answer with a diagram. f) Name an electromagnetic wave that can (i) Pass through metals (ii) Can cause a suntan (iii) Is used for radar (iv) Is emitted by warm objects (v) Is used by the human eye to see colour (vi) Is diffracted off buildings. Extension questions and homework Science Interactive LTD Copyright 2005 Total internal Reflection Reflection Three Two One Other examples Refraction Diagram

4: Complete the table: 5: a) Using radar apparatus, the wave echo takes 0.0002 seconds to travel from the source to the plane and back. Remembering that the speed of light is 300,000 kms -1 , how far away is the plane. b) What is the difference between a convex and a concave lens. Give an example of one device that uses (i) concave and (ii) convex reflectors. c) Light rays from the Sun takes approximately 8.7 minutes to travel from the Sun to Earth. Work out the distance in km between the two objects. d) What colour would a blue book look under (i) White light (ii) Blue light (iii) Green light (iv) Red light. 6: Ultraviolet, Gamma rays and radio rays are all part of the electromagnetic spectrum. Write down: a) Which has the longest wave length. b) Which has the highest frequency. c) Which is emitted by the nucleus of an atom. d) Two properties that they have in common 7: Complete the following: The full order of the electromagnetic spectrum is .__________________. The section with the longest wavelength is __________________. The waves that pass through metal are ________________ and those that damage your skin DNA causing cancer are _________________. Internet: Go to google.co.uk and find about how telescopes function, how they magnify distant images. Also find out about the use of optic fibres for communication and Broadband internet. Science Interactive LTD Copyright 2005 Red + Green Blue + Green Blue + Yellow Appearance Red + Blue Red + Green + Blue Colours of light added together