# Homework Help: Photon flux on surface.

1. Nov 30, 2007

### vagab0nd

1. The problem statement, all variables and given/known data
An area of 2 sq. meter is lit with power 10W/m^2 with light on wave length equal to 600nm.
What is the photon flux that HIT the 2 sq. meter surface.

2. Relevant equations
E=hv - plank const and frequency (c/lambda)
Photon flux of EMITTED source is flux=N/t=P/hv

3. The attempt at a solution
It seems, that somehow the emitted flux P/hv has to be connected with flux that hit the surface...

2. Nov 30, 2007

### OJones

It seems that the question is stated in terms of the intensity of light on the surface (a constant 10W/(m^2) - note that this is INTENSITY, not power). In this case there is no need to calculate the intensity of light falling on the surface from the power of the source - it is given in the question. In that case, it is simply a matter of finding the number of photons in the 20 Joules that reach the surface each second from the Planck's constant relation given, E=hc/l.