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Questions and Answers
What is one source of light energy that is man-made?
Light requires a medium to travel through.
False
What are the primary colors in the visible spectrum?
Red, Orange, Yellow, Green, Blue, Indigo, Violet
______ light is produced through exposure to UV energy.
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Match the type of light source with its description:
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Which color of light is the least energetic?
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Thomas Young demonstrated that light can show particle properties.
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What method of energy transfer occurs through a vacuum?
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What gas is used in an incandescent light bulb to help the filament burn?
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Fluorescent bulbs emit light while converting energy from UV sources.
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What process describes the emission of light due to high temperatures?
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When electrical current runs through the tungsten filament, it becomes _____ hot.
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Which of the following gases produces a red-orange color in neon lights?
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Match the following types of light emission with their definitions:
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What is the main reason why incandescent bulbs are considered inefficient?
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Materials that absorb UV light and emit visible light are known as _____
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Study Notes
Light: A Form of Energy
- Light is a visible form of energy that travels extremely fast, making it capable of circling the Earth’s equator roughly seven and a half times in a single second.
- Light originates from both natural and artificial sources:
- Natural sources: Sun
- Artificial sources: Flashlight
- Light travels in straight lines.
Sources of Light
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Luminous: Produce or give off their own light. Examples: Sun, turned-on flashlight.
- Incandescent: Emit light due to high temperatures achieved by friction, electricity, or chemical reactions.
- Fluorescent / Phosphorescent: Emit light after exposure to specific forms of radiant energy, such as UV energy.
- Gases Lit by Electrical Charge: Produce light when an electrical current flows through them. Examples: neon, argon, air (as in lightning).
- Non-Luminous: Reflect light but cannot create their own. Examples: Moon (reflects sunlight), metal shining when reflecting sunlight.
Light as an Electromagnetic Wave
- Light, unlike heat energy, does not require a medium to travel.
- Heat energy can be transferred by convection, conduction, and radiation:
- Conduction: Commonly occurs in solids.
- Convection: Commonly occurs in liquids and gases.
- Radiation: Method of energy transfer that doesn't need a medium, and energy travels at the speed of light.
- Thomas Young's experiment (1801): Demonstrated light's wave-like properties under specific conditions.
- Electromagnetic wave: A wave with both electric and magnetic components that travels at the speed of light without requiring a medium.
- Visible Light: Electromagnetic waves detectable by the human eye.
- ROY G BIV: Represents the colors of the visible spectrum: Red, Orange, Yellow, Green, Blue, Indigo, Violet.
Colors Associated with Visible Light
- Visible Spectrum: A continuous sequence of colors comprising white light (ROY G BIV).
- Prisms: Can separate white light into colors by slowing down the speed of light at different rates. Red, the least energetic color, is slowed the least, while violet, the most energetic, is slowed the most.
How is Light Produced?
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Incandescence: Process of emitting light due to high temperatures. Extremely hot objects become luminous.
- Incandescent Light Bulb: An electrical current heats the tungsten filament to a white-hot temperature, causing it to emit light.
- Efficiency: Only 5-10% of the electrical energy is converted to light in an incandescent bulb; the rest becomes infrared light, making it an inefficient light source.
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Electrical Discharge: Electricity passing through a gas produces light. Examples: neon lights, lightning.
- Neon Light: Different gases produce distinct colors when electricity flows through them. Neon gas emits red-orange, mercury vapor emits blue, helium emits gold, argon emits violet-blue, krypton emits grayish off-white.
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Phosphorescence: Materials (phosphors) emit light after absorbing energy from another source. Examples: glow-in-the-dark stickers.
- How it Works: Phosphors absorb light energy, especially UV light, store some of it, and release it as visible light of lower energy.
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Fluorescence: Emitting light while absorbing energy from a UV source. Examples: lasers, fluorescent tubes.
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Fluorescent Tube: A glass tube with a phosphorous coating on the inside and filled with mercury vapor. Electricity excites the mercury gas, generating UV light. This UV light then strikes the phosphorous coating, causing it to glow.
- Efficiency: Fluorescent bulbs are more efficient than incandescent bulbs, converting 4-5 times (20%) more electrical energy to light, resulting in less heat generation.
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Fluorescent Tube: A glass tube with a phosphorous coating on the inside and filled with mercury vapor. Electricity excites the mercury gas, generating UV light. This UV light then strikes the phosphorous coating, causing it to glow.
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Chemiluminescence: Converting chemical energy into light energy with minimal temperature change. Examples: glow sticks.
- How it Works: A plastic tube contains two separate chemicals. Bending the tube breaks a glass vial inside, allowing the chemicals to mix and react, producing light.
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Description
Explore the fascinating world of light through this quiz focused on its properties, sources, and behavior. Test your knowledge on luminous and non-luminous entities, and the science behind light emission. Perfect for students learning about energy and light concepts!
