# Photoelectric effect question

1. Jun 8, 2017

### Biker

1. The problem statement, all variables and given/known data
If blue and red light are used on a photoelectric cell and they both have the same intensity (Power per area). Choose the correct option from the following

2. Relevant equations
E = nhf
Intensity = power/area
Quantum effeciency = 100%

3. The attempt at a solution
if they have the same intensity as in same power per area then the number of photons reaching the cell differs. Red has more photons than blue light does. Thus red should have higher current.

a to d from left to right.
The correct answer was a, Was the question phrased wrong and they meant by intensity the number of photons reaching the plate per sec? Or did they neglect the small difference between the two currents?

2. Jun 8, 2017

In my text book when it speaks about photoelectric effect, and it mentions "same intensity" I am supposed to think of intensity as the number of photons reaching the surface every second.

3. Jun 9, 2017

### Biker

Yea I do that too, But in this question they insisted that it is power per area. I guess this question is just weird.

Thanks for help

4. Jun 9, 2017

You are welcome!

5. Jun 10, 2017

### rude man

Blue photons have more energy per photon than red ones (=hf). So I would not go with that view.

Also, the question IS weird since photocell reponse to frequency varies greatly with the componds used to fabricate the photocell.