Waves/Light

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Waves : 1 Dimensional Waves
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Light[edit]

Light moves in a vacuum at a speed of c_{vac} = 3 \times 10^8 \mbox{ m} \mbox{ s}^{-1}. In transparent materials it moves at a speed less than c_{vac} by a factor n which is called the refractive index of the material:

c = c_{vac} / n .

Often the refractive index takes the form

n^2 \approx 1 + \frac{A}{1 - (k/k_R )^2} ,

where k is the wavenumber and k_R and A are constants characteristic of the material. The angular frequency of light in a transparent medium is thus

\omega = kc = \frac{k c_{vac}}{n} \approx 
\frac{k c_{vac}}{\sqrt{1+A}}(1+ \frac{1}{2}\frac{A}{1+A}\frac{k^2}{k^2_R})

so the frequency increases slightly with increasing k. Typically, when k is near kR, the material becomes opaque.

Ultimately, this is due to resonance between the light and the atoms of the materials.


Waves : 1 Dimensional Waves
1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13
Examples - Problems - Solutions - Terminology