Question

A laser used to weld detached retinas emits light with a wavelength of 652 nm in pulses that are 20.0ms in duration. The average power during each pulse is 0.6 W. then,
A. the energy of each photon is `3.048xx10^(-19)J`
B. the energy content in each pulse is 12mJ
C. the number of photons in each pulse is nearly `4xx10^(15)`
D. the energy of each photon is nearly 1.9 eV

Answer 1

Correct Answer - A::B::C::D
Energy of photon, `E_0=(hc)/(lamda)`
`=(6.626xx10^(-34)xx3xx10^(8))/(652xx10^(-9))`
`=3.048xx10^(-19)J=1.905eV`
Energy content in each pulse is
`0.6Wxx20xx10^(-3)s`
`E_p=12xx10^(-3)J=12mJ`
The number of photons in each pulse is
`(E_p)/(E_0)=(12xx10^-3)/(3.048xx10^(-19))`
`=3.9xx10^(16)approx4xx10^(16)`