A ray of light traverses successively a series of plane interfaces, all parallel to one an...

A ray of light traverses successively a series of plane interfaces, all parallel to one another and separating regions of differing thickness and refractive index.

a. Show that Snell’s law holds between the first and last regions, as if the intervening regions did not exist.

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b. Calculate the net lateral displacement of the ray from point of incidence to point of emergence.

Figure 1