Question

The maximum velocity of electrons emitted from a metal surface is v. What would be the maximum velocity if the frequency of incident light is increased by a factor of 4?

• A. 2v
• B. > 2v
• C. < 2v
• D. Between 0v and 2v

Answer 1

The correct option is B > 2v

Using the Einstein's equation for photoelectric effect, in first case $\frac{1}{2}m{v}^2=h\nu -W$ where $\nu =$ frequency of incident light, $W=$ work function of metal.

In second case, $\frac{1}{2}m{v}^{\prime 2}=h\left(4\nu \right)-W=4(h\nu -W)+3W=4\times \frac{1}{2}m{v}^2+3W$

This equation indicates that $v^{\prime }>2v$