1.

Monochromatic light of frequency 6.0xx10^(14)Hz is produced by a laser. The power emitted is 2.0xx10^(-3)W. (a). What is the energy of a photon in the light beam? (b) How many photons per second, on an average are emitted by the source?

Answer»

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Solution :a.Each PHOTON has an energy
`E=h upsilon=(6.63.10^(-34)Js)(6.0xx10^(14)Hz)=3.98xx10^(-19)J`
b. If N is the number of photons emitted by the source per second, the power P transmitted in the BEAM equalsN times the energyper photon E, so that P = N E. Then
`N=(P)/(E )=(2.0xx10^(-3))/(3.98xx10^(-19))=5.0xx10^(15)` photons per second.


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