A ray of light passes through an equilateral prism such that an angle of incidence is equal to the angle of emergence and the latter is equal to (3/4) textth the angle of prism. The angle of deviation is

Question

A ray of light passes through an equilateral prism such that an angle of incidence is equal to the angle of emergence and the latter is equal to (3/4) textth the angle of prism. The angle of deviation is (A) 45° (B) 39° (C) 20° (D) 30°

Tardigrade Admin · Accepted Answer

Angle of incidence = angle of emergence ie, i=i Also, i=(3/4) × angle of equilateral prism =(3/4) × 60° =45° Thus, angle of deviation =i+i-A =(45°+45°-60°) =30°

Q. A ray of light passes through an equilateral prism such that an angle of incidence is equal to the angle of emergence and the latter is equal to $\frac{3}{4} th$ the angle of prism. The angle of deviation is

$4 5^{\circ}$

$3 9^{\circ}$

$2 0^{\circ}$

$3 0^{\circ}$

Angle of incidence $=$ angle of emergence
ie, $i = i$
Also, $i = \frac{3}{4} \times$ angle of equilateral prism
$= \frac{3}{4} \times 6 0^{\circ}$
$= 4 5^{\circ}$
Thus, angle of deviation $= i + i - A$
$= (4 5^{\circ} + 4 5^{\circ} - 6 0^{\circ})$
$= 3 0^{\circ}$

Q. A ray of light passes through an equilateral prism such that an angle of incidence is equal to the angle of emergence and the latter is equal to 43​th the angle of prism. The angle of deviation is

45∘

39∘

20∘

30∘