Question

Isosceles glass prism (µ = 1.57) with small
refracting angles () is placed in front of
parallel beam of rays incident normally
on its base (see figure). The size of the
base 2a = 5 cm. Light falls on a screen at
a distance of 100 cm from the prism with
a dark patch of width 1 cm near center of
screen. Find the value of the refracting
angle 

Answer 1

Answer:

Consider an isosceles prism with one refractive silvered surface. A ray of light is incident normally on the refractive face AB

consider the diagram incident ray and normal at Q are parallel,

Therefore,

α=2A

2α+A=180 ∘

Solve the above equations,

2(2A)+A=180 ∘

5A=180 ∘

A=36 ∘

α=180∘ −36∘

=72∘