How Light Travels

Front

Electromagnetic radiation Noun

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[uh-lek-troh-mag-net-ik ray-dee-ay-shun]

Back

Electromagnetic radiation

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A form of energy that travels as waves, consisting of vibrating electric and magnetic fields radiating from a source.

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Example: The image shows how electromagnetic radiation includes visible light, represented by different colors and wavelengths.

Front

Radiant energy Noun

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[ray-dee-uhnt en-er-jee]

Back

Radiant energy

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The energy that is transferred by electromagnetic waves, such as light, heat, or radio waves, through space.

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Example: The Sun emits radiant energy that travels to Earth as electromagnetic waves.

Front

Electromagnetic spectrum Noun

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[uh-lek-troh-mag-net-ik spek-truhm]

Back

Electromagnetic spectrum

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The complete range of electromagnetic waves classified according to their frequency and wavelength, from radio waves to gamma rays.

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Example: The image shows the electromagnetic spectrum, illustrating different waves from radio to gamma rays, with labels for frequency and wavelength.

Front

Wavelength Noun

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[wayv-length]

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Wavelength

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The distance between two consecutive corresponding points of a wave, such as from one crest to the next crest.

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Example: The image shows a wave with labeled crests and troughs, illustrating the wavelength as the distance between two crests.

Front

Frequency Noun

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[free-kwuhn-see]

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Frequency

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The number of complete waves that pass a specific point in a given amount of time, measured in hertz.

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Example: A wave diagram showing crests and troughs helps explain frequency by illustrating wave cycles.

Front

Intensity Noun

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[in-ten-si-tee]

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Intensity

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The amount of energy that a wave carries per unit area in a specific amount of time.

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Example: The diagram shows wave amplitude, which relates to intensity as energy carried by the wave.

Front

Medium Noun

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[mee-dee-uhm]

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Medium

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A substance or material, such as a solid, liquid, or gas, through which a wave can travel.

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Example: The image shows how waves travel through water, with labels for crest, trough, and wavelength.

Front

Vacuum Noun

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[vak-yoom]

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Vacuum

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A space that is empty of matter, through which electromagnetic waves are able to travel without a medium.

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Example: Light from the Sun travels through the vacuum of space to reach Earth.

Front

Speed of light Noun

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[speed uv lite]

Back

Speed of light

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The constant speed at which light and all other electromagnetic waves travel through a vacuum, about 300,000 km/s.

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Example: The image shows that light travels at a constant speed (c) regardless of the observer's motion, unlike other objects.

Front

Light ray Noun

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[lite ray]

Back

Light ray

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A narrow beam of light that travels in a straight line, used as a model to show the path of light.

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Example: Light rays reflecting off a surface show how light travels in straight lines.