Question

A particle with charge Q, moving with a momentum p, enters a uniform magnetic field normally. The magnetic field has magnitude B and is confined to a region of width d, where d < p/BQ.The particle is deflected by an angle θ in crossing the field.

(a) sin θ = BQd/p

(b) sin θ = p/BQd

(c) sin θ = Bp/Qd

(d) sin θ = pd/BQ

Answer 1

Correct Answer is: (a) sin θ = BQd/p

A to D is part of a circle with centre C.

CD = r. 

mv = p = BQr.

or r = p/BQ.

sin θ = ED/CD = d/r = BQd/p.