Question

A ray of light incident at an angle $\theta$on a refracting face of a prism emerges from the other face normally If the angle of the prism is 5⁰ and the prism is made of a material of refractive index 1.5,the angle of incidence is

• A. 7.5⁰
• B. 5⁰
• C. 15⁰
• D. 2.5⁰

Answer 1

Answer: (A)

7.5⁰

Answer 2

: According to the question, ray emerges from other surface of prism normally,

$\therefore$Angle of incidence at second face,

Now,

$\Rightarrow \mathrm { r } = \mathrm { A } - \mathrm { r } ^ { \prime } = 5 ^ { \circ } - 0 ^ { \circ } = 5 ^ { \circ }$

Using snell’s law

or

$\Rightarrow \theta = \mathrm { i } = \sin ^ { - 1 } ( 0.131 ) = 7.5$