- #1

dmriser

- 50

- 0

## Homework Statement

Calculate the average irradiance for the given laser beam.

λ=645nm, P=3mW, d=1mm.

## Homework Equations

S=[E X H]

S_avg = (1/2) * c * n * ε0 * E0^2

## The Attempt at a Solution

I understand the Poynting vector and I can derive the average irradiance formula. I cannot however find the field amplitude E_0 with the information I have.

I know that the field amplitude is proportional to photon flux, but I can't find anywhere what the constant of proportionality is.

First, I calculated the energy per photon.. 3 * 10^-19 J, then I find the photon flux by finding intensity (P/A). From this information I arrive at the photon flux.. From here I don't know what to do.

To be clear, I have something like this for photon flux: 1x10

^{19}photons/m

^{2}*s