A beam of protons with speed 4 × 105 ms–1
enters a uniform magnetic field of 0.3 T at an
angle of 60° to the magnetic field. The pitch of
the resulting helical path of protons is close to :
(Mass of the proton = 1.67 $ \times 10–27 kg, charge
of the proton = 1.69 \times $ 10–19 C)