Question

A ray of light is incident normally on the first refracting face of the prism of refracting angle A. The ray of light comes out at grazing emergence. If one half of the prism(shaded position) is knocked off, the same ray will-

• A. Suffer a deviation of A/4
• B. Not emerge out of the prism
• C. Emerge at an angle of sin^–1
• D. Emerge at an angle of emergence sin^–1

Answer 1

Answer: (D)

Emerge at an angle of emergence sin^–1

Answer 2

$\frac { \sin \mathrm { A } } { \sin 90 ^ { \circ } } = \frac { 1 } { \mu }$ Ž sin A = $\frac { 1 } { \mu }$

Now $\frac { \sin \mathrm { A } / 2 } { \sin \mathrm { r } } = \frac { 1 } { \mu }$

sin r = m sin A/2 =

sin r = $\frac { \sin \mathrm { A } / 2 } { 2 \sin \mathrm { A } / 2 \cos \mathrm { A } / 2 } = \frac { 1 } { 2 }$ sec A/2

r = sin^–1 $\left( \frac { 1 } { 2 } \sec \mathrm { A } / 2 \right)$