can anybody help me with this a level physics exam question?

Question

monochromatic light of wavelength 3.80 x 10-7m falls with an intensity of 6.0 x 10-6 W m-2 on to a metallic surface whose work function is 3.2 x 10-19J.

a) calculate the energy of a single photon of light of this wavelength
b) the number of photons emmited per second from 1.0 x 10-6 m2 of the surface if a photon has a 1 in 1000 chance of ejecting an electron.

please show me how to do it and not just give me the answer

Answer 1

The energy of a single photon is dependent only on its frequency and not on the intensity of the light source.

That energy = hc/l where:
h is Planck's constant
c is the speed of light in a vacuum
l is the wavelength of the photon

For b), it sounds like you really want the number of electrons emitted from a unit surface per unit time, and you are given a rate of one electron per 1000 photons, so all you have to do is calculate the number of photons per unit surface per unit time given the illumination intensity in watts per unit area.

If you know the energy per photon and the intensity in total energy per unit area per unit time, then you can compute the photons per unit area per unit time.