How Many Photons Are Emitted by a 100W Bulb per Second?

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Homework Statement



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.

Homework 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 \DeltaE=nhf where n is the number of photons.

The Attempt at a Solution



I get 2.5\times10^{20} photons/second
 
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You solved the problem correctly.
 

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