Quantity of photons emitted from a sodium lamp

[Eivind]

How many photons is sendt out per second from a 100 W natrium lamp, which gives a wawelenght of 589 nm(if 50% of the energi goes to the creation of light)?

I think I have to use photo elektric effect, but how?

Hints, anyone?

 

[Galileo]

You don't have to use the photoelectric effect. Each photon carries an energy determined by its wavelength. If you know the energy the lamp dissipates as light (per second) you can calculate how much photons that amounts to (per second).