Homework Help: physics

Posted by rick on Wednesday, April 16, 2008 at 10:31pm.

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.

physics - bobpursley, Wednesday, April 16, 2008 at 10:52pm
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.
- physics - rick, Wednesday, April 16, 2008 at 11:10pm
  still dont understand where does wavelength and number of photons go too? do you divdide them to get energy or what?
physics - bobpursley, Wednesday, April 16, 2008 at 11:13pm
You get energy per photon from Planck's equation, then multiply by the nubmer to get joules/second (watts).

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