Question

When an ultraviolet light is incident on a photocell, its stopping potential is $V_{0}$ and the maximum kinetic energy of the photoelectrons is $K_{m a x}$ . When $X$ -rays are incident on the same cell, then

• A. $V_{0}$ and $K_{m a x}$ both increase.
• B. $V_{0}$ and $K_{m a x}$ both decrease.
• C. $V_{0}$ increases but $K_{m a x}$ remains the same.
• D. $K_{m a x}$ increases by $V_{0}$ remains the same.

Answer 1

Answer: (A)

The frequency of $X$ - ray is higher than that of ultraviolet light.
Now, $K_{m a x}=h\left(v - v_{0}\right)$ .
Hence $K_{m a x}$ increases as $v$ is increased.
Also $K_{m a x}=eV_{0}$ , where $V_{0}$ is the stopping potential.