Properties of Light
By DarthVader
Date: 2022-07-13
Topic: 146 see comments
Post views: 1014
Properties of Light
When light waves strike a material or substance, there are three possible outcomes:
- The light can be ‘absorbed’, where the photons of light transfer their energy to the electrons of the atoms in the material for a while, before being re-emitted. Re-emitted light may have a different spectrum than that of the original light wave.
- The light can ‘pass through’ the material or substance.
- The light may be ‘reflected’ from the material.
Diffraction
Video: https://youtu.be/1bHipDSHVG4
The bending and spreading out of light waves (and also any other types of waves) as they pass through a ‘slit’ (or opening), or pass around the edge of an object (e.g. the spreading of light waves around an object).
d sinθ = nλ
where:
d = distance between slits
sinθ = diffraction angle
n = order number for the maximum
λ = wavelength
Refraction
Refraction - occurs as light changes direction when crossing the boundary between two mediums.
The refractive index of a material is calculated from:
n = sin i / sin r
where:
n = constant for a particular pair of media and a particular frequency of light
sin i = the angle of incidence, between the light ray and a line normal (perpendicular) to the materials surface
sin r = the angle of refraction, between the light ray and a line normal (perpendicular) to the surface in the same plane as the incident ray
Dispersion
Dispersion - occurs as light is split into its component colors when passing through a dispersive material.
The dispersive power can be calculated for light of any 2 wavelengths, 1 and 2, as:
D = (n1 − n2) / (n − 1)
where:
D = dispersive power
n1 = the refractive index of the material for wavelength 1
n2 = the refractive index for wavelength 2
n = the mean of n1 and n2
Scattering
Light ‘scatters’ as it hits a rough surface or impurities in a substance as it passes through e.g. the atmosphere.
Blue light scatters in the Earths atmosphere because it has a higher frequency, and therefore strikes more particles as it passes through the atmosphere, making the blue light ‘scatter’ more, making the sky look blue.
Reflection
Light waves change direction when they strike a reflective surface and therefore do not pass through or become absorbed by the material.
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