Physics - Magnetism Question with Solution | TestHub

The magnetic force acting on a moving charge is given by $\vec{F}=q(\vec{v}\times \vec{B})$.

Since the magnetic force is always perpendicular to the velocity vector, the work done by the magnetic field on the electron is zero.

According to the work-energy theorem, the kinetic energy of the electron remains constant, which implies its speed $v$ remains constant.

The de-Broglie wavelength is given by $\lambda =\frac{h}{mv}$.

Since the speed $v$ is constant, the de-Broglie wavelength of the electron remains constant.

Answer: remains constant.