2. A beam of light is incident on a slab of glass (n = 1.5) that is 4 cm thick.

Question

2. A beam of light is incident on a slab of glass (n = 1.5) that is 4 cm thick. The angle of incidence for the beam of light at the air-glass interface is 40 degrees and the glass has a mirror back. Find the distance between the point where the light initially enters the glass and where the light leaves the glass after reflecting from the back. 3. A ray of light is incident normally on the face of a glass prism (n=1.5). Assuming that the prism is in air, find the largest value for the angle theta so that the ray is totally reflected at the slanted side of the prism.

Explanation / Answer

a)Angle of refraction=r

By snell's law,

Sin 40/Sin r=1.5

r=29.8 degrees

Distance=2tSin r=2*4*Sin(29.8)=3.98cm

b)Angle of incidence on the angular face=90-theta

For TIR,

angle of incidence=Sin^-1(1/1.5)=41.8 degrees

90-theta=41.8

theta=48.2 degrees

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