Photoelectric Effect: Einstein's Equation question from JEE Main 2025 (2 Apr, Shift 1)

A monochromatic light is incident on a metallic plate having work function $\phi$. An electron, emitted normally to the plate from a point A with maximum kinetic energy, enters a constant magnetic field, perpendicular to the initial velocity of electron. The electron passes through a curve and hits back the plate at a point $B$. The distance between $A$ and $B$ is: (Given: The magnitude of charge of an electron is e and mass is $m, h$ is Planck's constant and c is velocity of light. Take the magnetic field exists throughout the path of electron)