v_{1} is responsible for horizontal motion of proton
v_{2} is responsible for circular motion of proton
Mass of proton = 1.67 * 10^{-27} Kg
Charge on proton= 1.6 * 10^{-19} C
∴ mv^{2}_{2} / r = qv_{2} B
r = mv_{2} /qB
= 1.67 * 10^{-27 * } 4 x 10⁵ / 1.6 * 10^{-19 * }0.3
= 0.013 m
Pitch of helix = v_{1} x T
Where T = 2πr / v_{2}
_{ } = 2πr / v sin θ
⇒ Pitch of helix = v cos θ x 2πr / v sin θ
= 2 πr cotθ
= 2x 3.14 x 0.013 x cot 60°
= 0.0471 m
= 47.1 mm