Question

A Light of wavelength $\lambda$ shines on a metal surface with intensity X, and the metal emits Y electrons per second of average energy Z. What will happen to Y and Z If X is doubled?

• A. Y will be doubled and Z will become half.
• B. Y will remain same and Z will be doubled.
• C. Both Y and Z will be doubled.
• D. Y will be doubled but Z will remain same.

Answer 1

The correct option is D

Y will be doubled but Z will remain same.

When know that,

In photoelectric effect:

$\to$ The number of electrons ejected are proportional to intensity of light

$\to$ Intensity does not affect average energy of photo-electrons.

Now, when intensity is doubled, the number of electrons emitted per second (Y) will be doubled.
Further - there will be no effect on the average energy of photo-electrons (Z).

$\Rightarrow$ Y $\to$ Doubled

Z $\to$ Same