If the white powder coating was not present inside a fluorescent lamp tube:
- The lamp would appear dimmer overall, as the powder coating converts invisible ultraviolet light from the gas into visible white light.
- There would be an unpleasantly bright white line near the center of the tube, as the mercury gas would emit its characteristic ultraviolet resonance line visible to the naked eye.
- The powder coating, or phosphor, absorbs the ultraviolet light and re-emits visible light, distributing it evenly along the tube for a brighter, more uniform glow.
Hi there,
In this presentation we have the complete details about the incandescent lamp and this presentation gives the complete history of the incandescent lamp or the history of the lamp. This presentation tells that what it have and what it is.....
I hope that you like this presentation........
Have A Nice Day
Yours Krishna.....
A fluorescent lamp tube is coated with a white powder on its inside surface. If that powder were not there, would the lamp appear brighter, dimmer, or about the same overall brightness
Hi there,
In this presentation we have the complete details about the incandescent lamp and this presentation gives the complete history of the incandescent lamp or the history of the lamp. This presentation tells that what it have and what it is.....
I hope that you like this presentation........
Have A Nice Day
Yours Krishna.....
A fluorescent lamp tube is coated with a white powder on its inside surface. If that powder were not there, would the lamp appear brighter, dimmer, or about the same overall brightness
Electrical Wiring:Types of wires and Cables and the circuit control on domest...maharshi solanki
Electrical Wiring:Types of wires and Cables and the circuit control on domestic installation
Prepared by: Maharshi Solanki
Guided by:Prof. Jaydeep Vanpariya
Electrical Wiring:Types of wires and Cables and the circuit control on domest...maharshi solanki
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Prepared by: Maharshi Solanki
Guided by:Prof. Jaydeep Vanpariya
Luminescence is the emission of light by a substance. It occurs when an electron returns to the electronic ground state from an excited state and loses its excess energy as a photon.
It is of 3 types.
Fluorescence spectroscopy.
Phosphorescence spectroscopy.
Chemiluminescence spectroscopy
Fluorescence spectroscopy. : When a beam of light is incident on certain substances they emit visible light or radiations. This is known as fluorescence. Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off. The substances showing this phenomenon are known as flourescent substances
Phosphorescence spectroscopy: When light radiation is incident on certain substances they emit light continuously even after the incident light is cut off.
This type of delayed fluorescence is called phosphorescence.
Substances showing phosphorescence are phosphorescent substances.
Chemiluminescence (also chemoluminescence) is the emission of light (luminescence) as the result of a chemical reaction. There may also be limited emission of heat
Fluorescence
Phosphorescence
Radiation less processes
Vibration relaxation
Internal conversion
External conversion
Intersystem crossing
Jablonski diagram is a graphical representation of the various transitions(electronic states, vibrational levels) that can occur after a molecule has been excited photochemically.
When a molecule is raised from its ground state to a higher state using light, photochemistry occurs.
The molecule in the excited state has a shorter lifetime and significantly more energy than the ground state from which it was formed.
As a result, molecules in the excited state are much more reactive.
A photochemical or photophysical process deactivates an excited state.
Therefore, the fate of the excited molecules is described by using the Jablonski diagram, which only focuses on the photophysical process occurring during the excitation and deactivation process.
Radiative transitions involve the absorption of a photon, if the transition occurs to a higher energy level, or the emission of a photon, for a transition to a lower level.
Nonradiative transitions arise through several different mechanisms, all differently labeled in the diagram. Relaxation of the excited state to its lowest vibrational level is called vibrational relaxation. This process involves the dissipation of energy from the molecule to its surroundings, and thus it cannot occur for isolated molecules. A second type of nonradiative transition is internal conversion (IC), which occurs when a vibrational state of an electronically excited state can couple to a vibrational state of a lower electronic state.
A third type is intersystem crossing (ISC); this is a transition to a state with a different spin multiplicity. In molecules with large spin-orbit coupling, intersystem crossing is much more important than in molecules that exhibit only small spin-orbit coupling. ISC can
Lohith will gives a brief overview of what electromagnetic radiation is all about.
About the speaker:
Lohith is 14 years old and is a part of Mango Astronomy club. He is passionate about physics.
What are the working principles of different artificial light sourcesErinChen37
Light is a form of radiant energy that travels in waves made up of vibrating electric and magnetic fields. These waves have both a frequency and a length, the values of which distinguish light from other forms of energy on the electromagnetic spectrum.
Visible light, as can be seen on the electromagnetic spectrum, represents a narrow band between ultraviolet light (UV) and infrared energy (heat). These light waves are capable of exciting the eye's retina, which results in a visual sensation called sight. Therefore, seeing requires a functioning eye and visible light.
This includes basic laser principles which are required to understand working of any laser system. It consists of the terms like excitation, de-excitation, population inversion, optical resonator, pumping source, active system and basic laser action.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
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Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Safalta Digital marketing institute in Noida, provide complete applications that encompass a huge range of virtual advertising and marketing additives, which includes search engine optimization, virtual communication advertising, pay-per-click on marketing, content material advertising, internet analytics, and greater. These university courses are designed for students who possess a comprehensive understanding of virtual marketing strategies and attributes.Safalta Digital Marketing Institute in Noida is a first choice for young individuals or students who are looking to start their careers in the field of digital advertising. The institute gives specialized courses designed and certification.
for beginners, providing thorough training in areas such as SEO, digital communication marketing, and PPC training in Noida. After finishing the program, students receive the certifications recognised by top different universitie, setting a strong foundation for a successful career in digital marketing.
2. Question:
A fluorescent lamp tube is coated with a white
powder on its inside surface. If that powder were
not there, would the lamp appear brighter,
dimmer, or about the same overall brightness, but
with an unpleasantly bright white line near its
center?
3. Observations About Fluorescents
• They often take a few moments to turn on
• They come in several variations of white
• They are often whiter than incandescent bulbs
• They last longer than incandescent bulbs
• They sometimes hum loudly
• They flicker before they fail completely
4. Seeing in Color
• Three groups of light sensing cone cells
• We perceive different colors when two or more type of
cone cells respond at once
5. Problems with Thermal Light
• Temperature too low, too red
– Incandescent light bulb, 2500°C
– The sun, 5800°C
• Not energy efficient
– Lots of invisible infrared light
– Only a small fraction of thermal power is visible
6. Fluorescent Lamps 1
• Glass tube, low pressure gas, electrodes
• Inject free charges via temperature or high voltage
• Forms a plasma—a gas of charged particles
• Electric field produces current flow in plasma
• Collisions cause
– electronic excitation in gas atoms
– some ionization of gas atoms
• Excited atoms emit light
through fluorescence
7. Atomic Structure
• In an atom, the electrons orbit the nucleus
• Only certain orbits are allowed—the orbitals
• Each orbital can have at most two electrons in it
• Orbital’s energy = kinetic + potential
• Electrons normally reside in the lowest energy
orbitals—the ground state
• Electrons can be excited to higher energy orbitals
—excited states
8. Atomic Structure
• Electrons travel as waves
• Electron in an orbital doesn’t emit light
• Electron emits light when changing orbitals
9. Light from Atoms
• Light
– travels as a wave (a diffuse structure)
– is emitted or absorbed as a particle (a photon)
• Photon energy = Planck constant · frequency
• An atom’s orbitals have specific energy differences
• Energy differences establish photon energies
• An atom emits a specific spectrum of photons
10. Electron/Atom Collisions
• An electron bounces off an atom
– Electron loses no energy → atom is unaffected
– Electron loses some energy → atom becomes excited
– Electron loses lots of energy → atom is ionized
11. Atomic Fluorescence
• Excited atoms lose energy via radiative transitions
• During transition, electrons shift to lower orbitals
• Photon energy is difference in orbital energies
– Small energy differences → infrared photons
– Moderate energy differences → red photons
– Big energy differences → blue photons
– Very Big differences → ultraviolet photons
• Atoms typically have bright “resonance lines”
• Mercury’s resonance line is at 254 nm, in the UV
12. Phosphors
• A mercury lamp emits mostly invisible UV light
• To convert its UV light to visible, use a phosphor
• Phosphors absorb photons and reemit new photons
• New photon energy is less than old photon energy
• Fluorescent lamps → phosphors emit white light
– (Deluxe) warm white, (deluxe) cool white phosphors
• Specialty lamps → phosphors emit colored light
– Blue, green, yellow, orange, red, violet, etc.
13. Question:
A fluorescent lamp tube is coated with a white
powder on its inside surface. If that powder were
not there, would the lamp appear brighter,
dimmer, or about the same overall brightness, but
with an unpleasantly bright white line near its
center?
14. Fluorescent Lamps 2
• Starting discharge requires electrons
• Heated filaments can provide electrons
– Manual preheat lamps (initial filament heating)
– Automatic preheat lamps (initial filament heating)
– Rapid start lamps (constant filament heating)
– Only rapid start lamps can be dimmed
• High voltages can provide electrons
– Instant start lamps (high voltage pulse start)
15. Fluorescent Lamps 3
• Gas discharges are unstable
– Gas is initially insulating
– Once discharge is started, gas become a conductor
– The more current it carries, the better it conducts
– Current tends to skyrocket uncontrollably
• Stabilizing discharge requires ballast
– Inductor ballast (old, 60 Hz)
– Electronic ballast (new, high frequency)
16. Low-Pressure Discharge Lamps
• Mercury gas emits ultraviolet resonance light
– Low pressure mercury lamps emit ultraviolet light
• Some gases emit visible resonance light
• Low pressure sodium emits yellow-orange light
– Very energy efficient
– Extremely monochromatic and unpleasant
17. Pressure Broadening
• High pressures broaden each spectral line
– Collisions occur during photon emissions
– Frequency and wavelength become less sharply defined
– Collision energy compensates for photon energy
18. Radiation Trapping
• Radiation trapping occurs at high densities
– Atoms emit resonance radiation very efficiently
– Atoms also absorb resonance radiation very efficiently
– Resonance radiation photons are trapped in the gas
– Energy can only escape discharge via other transitions
19. High-Pressure Discharge Lamps
• At higher pressures, new spectral lines appear
• High-pressure sodium emits richer light spectrum
– Still fairly energy efficient
– Not so monochromatic, more pleasant illumination
• High-pressure mercury emits nearly white light
– A little too blue, but good efficiency and color
• Adding metal-halides improves whiteness
– Nearly true white and good efficiency
Editor's Notes
Demonstration: Observe Incandescent Lamp Through Diffraction Grating and CCD Camera
Demonstration: Observe Gas Discharge Lamp (Neon) Through Diffraction Grating and CCD Camera
Demonstration: Observe Gas Discharge Lamp (Neon) Through Diffraction Grating and CCD Camera
Demonstration: Observe Gas Discharge Lamp (Helium) Through Diffraction Grating and CCD Camera
Demonstration: Observe Gas Discharge Lamp (Mercury) Through Diffraction Grating and CCD Camera
Demonstration: Phosphors and UV Lamp
Demonstration: Compare Uncoated Fluorescent Tube with Coated Tube
Demonstration: Show Various Fluorescent Lamp Fixtures