A non-relativistic free electron has kinetic energy K. If its wavelength doubles, its kinetic energy is:
A) 4 K
B) 2 K
C) still K
D) K/2
E) K/4

Question

Quizplus · Accepted Answer

The wavelength of a particle is inversely proportional to its momentum (de Broglie wavelength). If the wavelength doubles, the momentum is halved. Since kinetic energy is proportional to the square of momentum, the kinetic energy becomes one-fourth, or K/4.

A Non-Relativistic Free Electron Has Kinetic Energy K