Electrons are observed to be ejected in various directions with negligible speed from the negative plate of a parallel plate capacitor when the plate is illuminated by a certain wavelength. The plates are separated by a distance d and a potential difference V is maintained between them. Show that none of these electrons will reach the positive plate if a magnetic field is applied at right angles to the electric field and that the magnetic induction has a value `B gt ((2m V)/(ed^(2)))^(1/2)` where m and e are the electron mass and charge respectively.

Answer

A