JEE Main202125 Feb 2021Evening ShiftPhysicsMagnetic Effects of CurrentActual
An electron with kinetic energy K 1 enters between parallel plates of a capacitor at an angle α with the plates. It leaves the plates at angle β with kinetic energy K 2 . Then the ratio of kinetic energies K 1 : K 2 will be :
Options
- Asin 2 β cos 2 α
- Bcos β sin α
- Ccos β cos α
- Dcos 2 β cos 2 α
Correct answer
D. cos 2 β cos 2 α
Step-by-step solution
velocity along the plate will not change. ∴   v 1 cos α = v 2 cos β K 1   K 2 ⇒ v 1 2 v 2 2 = cos 2 β cos 2 α