Questions and Answers
What is the angle of reflection equal to in the Law of Reflection?
What is the purpose of a ray diagram?
What type of image is formed by rays that appear to be coming from a certain position, but are not actually coming from this position?
What is the term for the change in direction of a light ray when it bounces off a surface?
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What is the normal in a ray diagram?
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What happens to the image in a plane mirror?
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What is the term for the substance through which light travels?
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What is the characteristic of an image formed by a plane mirror?
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What is the process by which hydrogen atoms in the Sun's core release vast amounts of energy?
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What is the type of light emitted by a material when it is at a high temperature?
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What is the process by which mercury atoms emit ultraviolet light?
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What is the term for light that is generated without heating the object?
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What is the type of light that is generated by a biochemical reaction in a living organism?
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What is the term for the distance from one crest to the next in a light wave?
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What is the speed of light in a vacuum?
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What type of light uses less energy and lasts longer than incandescent light?
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Study Notes
Sources and Nature of Light
- All sources of light involve absorbing energy to raise atoms to an excited state, which then release energy as light.
- In the Sun's core, hydrogen atoms collide and fuse to form helium, releasing vast amounts of energy in the form of light through fusion reactions.
Types of Light
- Incandescent light is emitted when a material is heated to high temperatures, such as in incandescent light bulbs.
- Fluorescence occurs when a source is exposed to ultraviolet light, causing phosphor to emit visible light.
- Electrons excite Mercury atoms, which release UV light.
- UV light excites phosphor, producing visible light.
- Fluorescent lights are energy-efficient and last longer than incandescent bulbs.
- Luminescence is light generated without heating an object, using energy from various sources.
Phosphorescence and Chemiluminescence
- Phosphorescence is a type of luminescence where excited atoms retain energy for minutes to hours.
- Many glow-in-the-dark objects contain phosphorescent materials.
- Chemiluminescence is light generated by energy released in a chemical reaction without a rise in temperature, such as in glowsticks.
Bioluminescence
- Bioluminescence is light produced by a biochemical reaction in a living organism.
Properties of Light
- Light is the only form of energy that can travel as a wave through empty space and some materials.
- Light waves are electromagnetic waves that travel at 3 x 10^8 m/s in a vacuum.
- Wavelength is the distance between two consecutive crests.
- Electromagnetic spectrum is a diagram that illustrates the range of electromagnetic waves, ordered by wavelength or frequency.
Reflection
- Reflection is the change in direction of a light ray when it bounces off a surface.
- Light travels in a straight line in the same medium.
- Medium is the substance through which light travels.
- Ray diagrams can be used to make predictions about object appearances.
Law of Reflection
- The incident ray, reflected ray, and normal always lie on the same plane.
- The angle of reflection is equal to the angle of incidence (∠reflection = ∠incidence).
Mirrors
- Plane mirror has a flat reflective surface.
- Virtual image is an image formed by rays that appear to come from a certain position, but do not actually come from that position.
- Image does not form a visible projection on a screen.
- Our brain thinks the light rays are coming straight from an object behind the surface.
- Lateral inversion occurs in plane mirrors, where the image is reversed left to right.
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