# Homework Help: Multiple choice conceptual question on the photoelectric effect

1. Dec 2, 2012

### Duderonimous

1. The problem statement, all variables and given/known data
In a photoelectric effect experiment, the frequency of the light is increased while keeping the intensity of the light constant. What effect does this have?

A) fewer electrons will be ejected
B) more electrons will be ejected
C) the same number of electrons will be ejected
D) any of these is possible

2. Relevant equations
None.

3. The attempt at a solution
I know that if the frequency of the incident light on the metal is increased this will cause the stopping potential of the electrons emitted to increase, whilst keeping the intensity of the light constant. If the intensity of the incident light on the metal is increased this cause the number electrons emitted per time to increase but the stopping potential remains the same.

So if the frequency is increased but the intensity is constant wont the number of electrons emitted be constant? I picked C but it was marked wrong. Can someone please clarify this. Thanks.

2. Dec 2, 2012

### TSny

What happens to the energy of each photon when the frequency is increased?

What happens to the number of photons per second striking the plate as the frequency is increased and the intensity is kept constant?

3. Dec 3, 2012

### Duderonimous

The energy of each photon is increased.

less photons per second but each photon is more energetic, thus fewer electrons are emitted but each electron has a greater stopping potential.

4. Dec 3, 2012

Sounds good!