Consider a normal incidence of a monochromatic plane wave on a plan-parallel gla
ID: 1557415 • Letter: C
Question
Consider a normal incidence of a monochromatic plane wave on a plan-parallel glass slab in vacuum. (a) What parameters of the system will dictate what portion of optical power is transmitted through the slab? (b) The refractive index of glass is 1.5. Calculate the reflection and transmission coefficients for the vacuum-glass interfaces. (c) What is the maximum possible fraction of optical power transmitted through the slab? (d) What is the minimum possible fraction of optical power transmitted through the slab? (e) What is the minimum possible fraction of optical power reflected from the slab? (f) What is the maximum possible fraction of optical power reflected from the slab?Explanation / Answer
(a)
The reflection coefficient R is defined as the ratio of reflected power to the incident power
The transmission coefficient T is defined as the ratio of transmitted power to the incident power
The relation between reflection coefficient (R) and transmission ceofficient (T) is
R + T = 1 .................... (Assuming that the glass slab does not absorb any of the incident radiation)
The parameters affecting the reflection and transmission for a vacuum-glass slab boundary are their refractive indices (say nv and nr) respectively and the angle of incidence i and the angle of refraction r.
For normal incidence, the relation is as below:
R = ( nv - nr )2 / ( nv + nr )2
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(b) Here nv = 1 (vacuum) and nr = 1.5 (given) Hence R = 0.04 Thus, T = 0.96
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