Question

A right-angled prism of apex angle $4^{\circ }$ and refractive index $1.5$ is located in front of a vertical plane mirror as shown in figure. A horizontal ray of light is falling on the prism. Find the total deviation produced in the light ray as it emerges $2nd$ times from the prism.

• A. $8^{\circ }CW$
• B. $6^{\circ }CW$
• C. ${180}^{\circ }CW$
• D. ${174}^{\circ }CW$

Answer 1

Answer: (D)

${174}^{\circ }CW$

Deviation produced by prism is
${\delta }_1=(\mu -1)A=2^{\circ }CW$
Angle of incidence for mirror is ${\delta }_1$, so deviation produced by the mirror is
${\delta }_2=\pi -2{\delta }_1={176}^{\circ }CW$
Deviation produced by the prism for $2^{nd}$ refraction is
${\delta }_3=2^{\circ }ACW$
Net deviation $={174}^{\circ }CW$.