Question

A ray is incident at an angle i on the surface of a prism with very small prism angle A, and emerges normally from the opposite surface. If the refractive index of the prism is μ the angle of incidence i is nearly equal to ______ .
(A) A/μ
(B) μA/2
(C) A/2μ
(D) μA

Answer 1

2ℓ = 20 cm,Also, m x 2ℓ = 0.7 m ,

⇒ m = 14.4 / 20 cm

= 57.6 A-m2,

Torque due to magnetic field, = pm x B x sin 60°,

= 14.4 x 0.25 x √3/2,

The torque due to the force,= F x 0.12,

For equilibrium F x 0.12 = 14.4 x 0.25 x √3/2

⇒ F = 16.08 N .If the force F is removed, the torque due to magnetic field will move the bar magnet. It will start oscillating about the mean position.