# what happens to photo electric current when frequency increases and the intensity remain constant

I want to know what happens to the photoelectric current when frequency increases at constant intensity I have 2 answers I just need to verify:

1. Decreases because when energy of a photon increases increasing the size of a photon resulting less photons collide per unit time so it decreases

2. Constant because when the energy increases the size cant increases cos they are discrete particles so same amount of electrons ejected resulting noo change in the current

It's the second answer because you have explicitly said that the intensity is constant and the number of electrons, emitted by a surface is proportional to the intensity and independent of the frequency(one of the laws of the photo-electricity).

Assuming the frequency in the experiment is always above the threshold required for ionization...

I believe intensity is measured as energy transfer per second. Thus, if you increase frequency and keep intensity constant, the energy per photon increases, so the number of photons must decrease to keep the total energy transfer constant. The number of electrons released is proportional to the number of photons hitting the surface, so that would decrease, and the current would as well.

If intensity is measured as number of photons per second, then there would be no change.

From what I understand, you have electrons energized by photons leaving one plate and attempting to cross to another plate at a higher potential. Therefore, in order to get to the second plate the photons must have more energy. Energy of a photon is given by:

$$E = hf$$

If you increase the frequency, the photon will have more energy and can therefore transfer more electrons to the other side. As such, you will have an increased current.

• ?? the whole point is that it is a threshold effect, the ionisation, once the frequency is crossed each photon can kick out *one electron *, whose energy increases, but not the electron number hyperphysics.phy-astr.gsu.edu/hbase/mod2.html – anna v Mar 3 '18 at 5:57