Magnetron strength in field??

Question

i'm so confused on this one..

The magnetron

A magnetron is a microwave source in which a "bunch" of electrons travel on a circular orbit in a uniform magnetic field. As the electrons pass the electrodes, a high-frequency alternating voltage difference occurs.

Suppose the resonant frequency is f = 1.74×1010 s−1; that is, the electron period of revolution is T = 5.75×10-11 s. What is the corresponding strength of the magnetic field?

Answer 1

The cyclotron frequency formula is this:

f = (B * q ) / (2 * pi * m)

where q is the charge on the particle, m is the mass of the particle, and B is the magnetic field.

You can look it up in your textbook or on Wikipedia, under "cyclotron."

The magnetic field strength is therefore:

B = 2 * pi * f * m / q.

Plug and chug. (Google calculator says roughly 0.622 tesla.)