Question

A beam consisting of protons and electrons moving at the same speed goes through a thin region in which there is a magnetic field perpendicular to the beam. The protons and the electrons
(a) will go undeviated
(b) will be deviated by the same angle and will not separate
(c) will be deviated by different angles and hence will separate
(d) will be deviated by the same angle but will separate

Answer 1

(c) will be deviated by different angles and hence will separate

Force on a charged particle, F = qVB
For an electron, this force is F = $-$eVB, whereas on a proton this force is F = eVB.
Here, 'e' is the charge of the electron. So, from the above formulas, we can see that electrons and protons will experience equal force but in opposite directions; so they separate out. In other words, we can say that they are deviated by different angles and causes them to separate.