Illumination

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Electromagnetic Radiation Noun

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[eh-lek-tro-mag-net-ik ray-dee-ay-shun]

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Electromagnetic Radiation

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A form of energy, such as light, that can be modeled as a wave of changing electric and magnetic fields.

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Example: This diagram displays the electromagnetic spectrum, a range of energy waves. It highlights visible light, the part we see, which is essential for illumination.

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Photon Noun

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[foh-ton]

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Photon

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A particle representing a quantum of light or other electromagnetic radiation, which carries energy proportional to the radiation frequency.

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Example: This image shows photons, which are particles of light, hitting a metal surface and knocking electrons out, demonstrating how light transfers energy.

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Ray Optics Noun

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[ray op-tiks]

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Ray Optics

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The study of light interacting with matter, where light is modeled as traveling in straight lines called rays.

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Example: A light ray from a source hits a mirror and reflects. This shows the law of reflection, where the angle of incidence equals the reflection angle.

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Luminous Source Noun

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[loo-mi-nus sors]

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Luminous Source

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An object, such as the Sun or a lightbulb, that produces and emits its own light energy.

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Example: The sun is a luminous source because it is a natural object that produces and emits its own light, unlike the moon which only reflects light.

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Illuminated Source Noun

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[ih-loo-mi-nay-ted sors]

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Illuminated Source

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An object, such as the Moon, that is visible because it reflects light from another source.

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Example: This diagram shows the Moon, which is an illuminated source because it does not create its own light but is visible by reflecting sunlight.

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Opaque Adjective

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[oh-payk]

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Opaque

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A property of a medium that reflects and absorbs light but does not transmit it, preventing clear sight through it.

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Example: An opaque object blocks light from passing through it, which causes a shadow to form on the other side.

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Translucent Adjective

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[trans-loo-sent]

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Translucent

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A property of a medium that transmits and reflects light but does not allow objects to be seen clearly through it.

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Example: A translucent material scatters light rays from a flashlight, allowing some light to pass through but blurring any image behind it.

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Transparent Adjective

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[trans-pair-ent]

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Transparent

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A property of a medium that transmits most of the light that reaches it, allowing objects to be seen clearly.

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Example: A transparent material, like the glass in this window, allows light to pass through it completely, so you can see clearly to the other side.

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Luminous Flux Noun

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[loo-mi-nus fluks]

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Luminous Flux

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The rate at which a luminous source produces light energy, which is measured in the SI unit of lumens (lm).

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Example: A light source, like a bulb, emits a total amount of visible light in all directions; this total light energy is called luminous flux.

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Lumen (lm) Noun

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[loo-men]

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Lumen (lm)

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The SI unit of luminous flux, representing the total quantity of visible light emitted by a source per second.

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Example: This chart shows that different light bulbs can produce the same amount of brightness (800 lumens) while using different amounts of energy (watts).