Photons/Second from a 100W bulb.

1. Jun 16, 2011

Brammo

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

Estimate how many photons of visible light (500 nm) are emitted by a 100 W Bulb.

The answer on the sheet says approximately 10$^{20}$ photons/second

However when I work it out I get a slightly different answer.

2. Relevant equations

I used that 1J=1W/s or E=P/t

Also Energy of one photon is E=hf so if you had lots of photons you would $\Delta$E=nhf where n is the number of photons.

3. The attempt at a solution

I get 2.5$\times$10$^{20}$ photons/second

2. Jun 16, 2011

G01

You solved the problem correctly.