Question

A laser emits 1.44*10^18 photons per second in a beam of light that has a diameter of 1.98 mm and a wavelength of 524.5 nm.
(a) Determine the average electric field strength
(b) Determine the average magnetic field strength for the electromagnetic wave that constitutes the beam.

Answer 1

You know the energy (given wavelenght and the number of photons)

http://en.wikipedia.org/wiki/Poynting_vector

You know the Poynting vector (watts/m^2) in the beam, so figure E and B.
check my thinking.

Answer 2

still don't understand where does wavelength and number of photons go too? do you divdide them to get energy or what?

Answer 3

You get energy per photon from Planck's equation, then multiply by the nubmer to get joules/second (watts).