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Light

lastmod 2025-03-12created 2021-01-2117 edits

Wave nature of light (interference)

Properties of waves

Reflection
The phenomenon in which a wave traveling through one medium changes direction at the boundary with another medium and travels back into the original medium
Refraction
The phenomenon in which a wave traveling through one medium changes direction at the boundary with another medium and travels into the other medium
Diffraction
The phenomenon in which a traveling wave bends around a narrow gap or the edge of an obstacle. It occurs more readily the narrower the gap and the longer the wavelength.

Wave interference

The change in amplitude when two or more waves overlap

Constructive interference
When the displacements of the overlapping waves are in the same direction, so the displacement of the resulting wave increases
Destructive interference
When the displacements of the overlapping waves are in opposite directions, so the displacement of the resulting wave decreases

Types of light

Ambient light (ambient)
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Diffuse light (diffuse)
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Reflected light (specular, reflected light)
Specular reflection - Reflection that occurs at a mirror-smooth surface.
Diffuse reflection - Light entering a surface is reflected in many directions.

AG (Anti-Glare) vs AR (Anti-Reflection)

Both AG and AR are features for preventing glare. However, they differ in how they prevent it.

  • AG scatters light to reduce the light reflected from the reflecting surface that reaches your eyes,
  • AR cancels out light to reduce reflection.

So the specular reflectance is said to be 2–2.5% for AG and usually 0.5% or less for AR.

The laptop screens we commonly use are AG-treated, and AR can be found on eyeglasses. (If you look at light reflected off eyeglasses, you can see that it is not white light.)

Color temperature

Color_temperature.png

Lighting_Selection_Guide.jpg

See also

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