How many photons per second are emitted from the laser?

Question

A red laser pointer emits light at a wavelength of 635nm. If the laser emits 7.5 x 10^ -4 J of energy per second the form of visible radiation, how many photons per second are emitted from the laser?

Answer 1

You need to determine the energy of each photon first, by taking the wavelength (converted into m, 6.35 X 10^-7 m) and plug it into the equation c = frequency X wavelength (c = 3.00 X 10^8 m/sec) to solve for frequency. Then take the frequency you calculated and plug it into the equation energy = frequency X Planck's Constant (6.6 X 10^-34 J/Hz) to calculate the energy of one photon (if you did it right, you should get something X 10^-19J).

Then, take the joules emitted per second (7.5 X 10^-4) and divide it by the number of joules you calculated (which is actually Joules per photon) and the units simplify to photons/second.

Good luck!

Answer 2

just look up the energy of one electron at that wavelength and divide

the looking up and understanding what's going on is, I think, the part you are supposed to do

Answer 3

www.wikipedia.org
if the answer is not there there is no answer