Question

A parallel beam of monochromatic light of wavelength 663 nm is incident on a totally reflection plane mirror. The angle of incidence is `60^@` and the number of photons striking the mirror per second is `1.0xx10^19`. Calculate the force exerted by the light beam on the mirror.
A. `10nN`
B. `1000pN`
C. `10sqrt(3)nN`
D. `100sqrt(3)muN`

Answer 1

Correct Answer - A
`F=(dp)/(dt)=([mv costheta-(-mv costheta)]dn)/(dt)`
`=2mv cos 60((dn)/(dt))=mv((dn)/(dt))=(h)/(lambda)((dn)/(dt))=10^(-8)N`