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KCET · Physics · Ray Optics

A ray of light passes through an equilateral glass prism in such a manner that the angle of incidence is equal to the angle of emergence and each of these angles is equal to \(\frac{3}{4}\) of the angle of the prism. The angle of deviation is

  1. A \(39^{\circ}\)
  2. B \(20^{\circ}\)
  3. C \(30^{\circ}\)
  4. D \(45^{\circ}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(30^{\circ}\)

Step-by-step Solution

Detailed explanation

For an equilateral glass prism,
Angle of prism, \(A=60^{\circ}\)
If \(i\) and \(c\) be the angle of incidence and angle of cmergence respectively, then
\(i=\frac{3}{4} A=\frac{3}{4} \times 60^{\circ}=45^{\circ} \text { and } e=i=45^{\circ}\)
For a prism, we know that
\(\begin{aligned}A+\delta & =i+c \Rightarrow \delta=i+e-A \\\delta & =45^{\circ}+45^{\circ}-60^{\circ}=90^{\circ}-60^{\circ}=30^{\circ}\end{aligned}\)