14 Questions
What is the minimum temperature at which virtually all substances start to glow visibly in the dark?
470 °C
Chemiluminescence produces a significant amount of heat.
False
What is the process by which a substance absorbs energy and releases it slowly in the form of light?
Phosphorescence
The emission of light by a living organism is known as _______________.
Bioluminescence
What percentage of electricity is converted to light in an incandescent light bulb?
5-10%
Match the following types of light emission with their descriptions:
Incandescence = Emission of light due to heat Chemiluminescence = Emission of light due to a chemical reaction Bioluminescence = Emission of light by a living organism Phosphorescence = Emission of light due to slow release of energy
Fluorescence is the emission of light by a substance that has absorbed light of a different wavelength.
True
What is the common application of fluorescence?
Fluorescent tubes
What is the primary advantage of CFL lighting compared to incandescent technology?
Very energy-efficient
Scientists have a complete understanding of the phenomenon of triboluminescence.
False
What is the process by which LEDs emit light?
electroluminescence
The tube in a CFL is lined with a coating of a fluorescent material, called the ____________________.
phosphor
Match the following lighting technologies with their characteristics:
CFL = Very energy-efficient LED = Longer lifetime and smaller size Incandescent = Less energy-efficient
What is the color of the glow typically seen in triboluminescence?
Blueish, blueish-greenish, or white
Study Notes
Incandescence
- Emission of light from a hot body due to its temperature
- Substances start to glow visibly in the dark around 470 °C with a very dull red color
- Incandescent light bulbs work by resisting the flow of electrons, heating the filament, and emitting visible radiation (5-10% of electricity) and infrared radiation (90-95% of electricity)
Chemiluminescence
- Emission of light caused by a chemical reaction
- Produces little or no heat
- Occurs in glow sticks, where two chemicals mix to release light
Bioluminescence
- Production and emission of light by a living organism
- Essentially chemiluminescence, but in living organisms
- Found in marine vertebrates and invertebrates, microorganisms, and terrestrial animals
Phosphorescence
- Process of energy absorption and slow release in the form of light
- Causes "glow-in-the-dark" effect
- Energy is absorbed by exposure to ultraviolet light and stored for a longer time
Fluorescence
- Emission of visible light by a substance that has absorbed light of a different wavelength
- Release of energy is almost immediate
- Occurs in fluorescent tubes, where ultraviolet light is absorbed and re-emitted as visible light
Light-Emitting Diode (LED)
- Electronic light source that works by electroluminescence
- Electrons recombine with holes to release energy in the form of light
- Advantages: lower energy consumption, longer lifetime, improved robustness, smaller size, faster switching, durability, and reliability
Triboluminescence
- Optical phenomenon where light is generated when crystals are broken or deformed
- Scientists do not fully understand the mechanism, but it is believed to involve the separation of electric charges and recombination sparks
- Appears as a blueish, blueish-greenish, or white glow
Understanding the concept of incandescence, where hot bodies emit light, and its application in incandescent light bulbs.
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