Problem database

A magnetic field in a television tube rotates electrons with energy $E = 2 \cdot 10^4$ eV by an angle $\alpha = 60^\circ$ . The deflecting coil creates a magnetic field on a section of the tube with a length of $l = 10$ cm. Determine the magnetic field induction. What error is made when calculating the induction, if we ignore the changes in the mass of the electron during its movement?