What is the magnitude of the magnetic field?

n_h0987

1. The problem statement, all variables and given/known data

The nucleus of a Tl atom (Atomic mass = 203, element #81) has a magnetic moment of 1.611 µn. A magnetic field is applied to it and its NMR frequency determined to be 3.90 MHz. What is the magnitude of the magnetic field?

2. Relevant equations

torque = magnetic moment x magnetic field
radius = mv/qB
v = rw
Fcentripetal = mv^2/r

3. The attempt at a solution
I tried (magnetic moment x magnetic field)/radius = mv^2/r but this always leaves me with r in the equation, which is unknown.

Redbelly98

You can try looking in your textbook, or do an online search, for "Larmor precession" or "precession of magnetic moment" or something along those lines.