At what average rate would a hydrogen atom have to scatter visible
(
Å) photons directed at it from below
in order to suspend it against the earth's gravity? (Assume that the
atom scatters each photon in a random directions.)
Explain why you may ignore the Compton shift in solving
this problem. How much net momentum is transfered to the atom from
the photons during each minute on average? By what percentage
do we expect the actual momentum transfer in each minute to
deviate from the average value?
If, instead, we intend to suspend a tank of mass m=10,000 kg where the bottom of the tank is a perfect reflecting mirror, how many photons per second must we send at the tank? What power (in Watts) is needed to produce such a beam?