(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

a) Determine the momentum of a photon of light of wavelength 400nm.

b) A mass of 1mg is being held up by a beam of 400nm light. How many photons per second would have to hit the mass (from below) to do this, assuming the photons bounce back with the same momentum as they hit.

2. Relevant equations

a) p=h/(wavelength)

b) F=mg

3. The attempt at a solution

a) p=6.64x10^-34/400x10^-9=1.66x10^27 kgm/s

b) F=10^-3x9.81=9.81x10^-3N

I can only figure out how much force is needed to keep the mass still, I don't see how p and F are related :(

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# Homework Help: Photon Force

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