Unpolarized light in air is incident on a body of water ( nw = 1.33) such that t

Question

Unpolarized light in air is incident on a body of water (nw = 1.33) such that the reflected light is completely linearly polarized.

(a) What is the angle of incidence?

(b) The transmitted light hits a block of glass (ng = 1.5) located some distance under the surface of the water. Again, the light reflected from the glass is completely linearly polarized. What is the angle between the water and glass surfaces?

(c) Imagine that instead of hitting a single block of glass, the light transmitted into the water hits a stack glass plates (oriented at the angle found in Part (b)) separated by thin layers of water. Calculate the number of plates necessary to give rise to a polarization extinction ratio of 20 dB (in intensity) at the output.

Explanation / Answer

Given refractive index of   water n_w = 1.33   When unpolarized light is incident at this angle, the light that is reflected from the surface is therefore perfectly polarized . Brewesters angle is an angle of incidence at which light with a particular polarization is perfectly transmitted through a surface, with no reflection            angle of incidence         ? = tan ^ -1 ( n _2 / n_1 )                 = tan ^ -1 ( 1.33/1)                 = 53.06 ^ o angle between water and glass surface                n_1 sin ? = n_2 sin ?_1                   sin ?_1   =   ( n_1 / n_2 ) sin ?                                = ( 1 / 1.33 ) sin 53.06                             ?_1   =   36.93 degrees                            

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