Question

An equilateral prism is lying on the prism table of a spectrometer in a minimum deviation position. If the angle of incidence is ${60}^{\circ }$, then the angle of deviation will be :

• A. ${90}^{\circ }$
• B. ${60}^{\circ }$
• C. ${45}^{\circ }$
• D. ${30}^{\circ }$

Answer 1

Answer: (B)

${60}^{\circ }$

Deviation $=i+i^1-A$
for minimum deviation
$i=i^1$
so, $\delta =i+i-A$
$={60}^0+{60}^{{}^0}-{60}^0$
$={60}^0.$ Hence correct option is B.