# In a cyclotron, a magnetic induction of 1.4 T is used to accelerate

In a cyclotron, a magnetic induction of 1.4 T is used to accelerate protons. How rapidly should the electric field between the dees be reversed?

A. 5.2 × 10^-8 s

B. 2.34 × 10^-8 s

C. 792.25 × 10^-8 s

D. 46.25 × 10^-8 s

I got this question in unit test.

My question is from Motion in Combined Electric and Magnetic Field in section Moving Charges and Magnetism of Physics – Class 12

The correct answer is B. 2.34 × 10^-8 s

The best I can explain: Time period, t = $$\frac {\pi m}{qB}$$

t = $$\frac {(3.14 \, \times 1.67 \, \times \, 10^{-27})}{(1.6 \, \times \, 10^{-19} \, \times \, 1.4)}$$

t = 2.34 × 10^-8 s