Q.

A proton with a kinetic energy of 2.0 eV moves into a region of uniform magnetic field of magnitude π2×10-3 T. The angle between the direction of magnetic field and velocity of proton is 60°. The pitch of the helical path taken by the proton is _______cm. (Take, mass of proton =1.6×10-27 kg and charge on proton =1.6×10-19 C.)                     [2023]


Ans.

(40)

B=π2×10-3

K.E.=12mv2    v=2 K.E.m

Pitch=v cos 60°×time period of one rotation

           =v cos 60°×2πmeB

           =2×2×1.6×10-191.6×10-27×cos60°×2π×1.6×10-271.6×10-19×π2×10-3

            =2×104×12×4×10-5

             =4×10-1 m=40 cm