# Homework Help: Photons per second from lightbulb

1. Mar 31, 2015

### Kavorka

1. The problem statement, all variables and given/known data

If 5 percent of the power of a 100 W bulb is radiated in the visible spectrum, how many visible photons are radiated per second?

2. Relevant equations

E=hf=hc/λ

3. The attempt at a solution

I know how to solve this, I just wanted to make sure.
I will take 5 W or J/s as the power of the visible light, and once you know the energy of the visible light's photon in Joules finding the photons/second is easy. I am wondering though if it would be better to present a range of photons per second since the visible spectrum is a range of frequencies/wavelengths, or an average. The question seems like it wants a single answer.

2. Mar 31, 2015

### Kavorka

um

3. Mar 31, 2015

### SammyS

Staff Emeritus
Surely you could find a range. Then pick some reasonable answer in the middle.

You might assume white light - so an even distribution of frequencies, The energy is proportional to the frequency, so you get a nice energy distribution. Integrate over that someway.

Want to make things even more complicated? - - -

4. Mar 31, 2015

### Kavorka

Haha that's alright. I found a range as well as the average and will list those both, hopefully that is a satisfactory answer.