A beam of protons enters a uniform magnetic field of `0.314` T with a velocity `4xx10^(5)` `ms^(-1)` in a direction making an angle `60^(@)` with the direction of the magnetic field. The path of the beam is (mass of proton = `1.6xx10^(-27)`kg)

Options

A. a circle of radius 0.2 m
B. a straight line
C. a helix with a pitch 4 cm
D. a helix with a pitch 4 mm

Answer

C

Explanation

As , V is not prependicular to B, so path of particle is helix.
Pitch of helical path `=vcosthetaxx(2pim)/(Bq)`
`4xx10^(5)xx1/2xx(2xxpixx1.6xx10^(-27))/(0.314xx1.6xx10^(-16))`
=4cm