A 100W sodium lamp radiates energy uniformly in all directions. The lamp is located at the center of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is 589nm. (a) What is energy associated per photon with the sodium light? (b) At what rate are photons delivered to the sphere?

Options

A. `3xx10^(15)`
B. `3xx10^(10)`
C. `3xx10^(20)`
D. `3xx10^(19)`

Answer

C

Explanation

(c ) : Here `lamda=589xx10^(-9)m,h=6.63xx10^(-34)J` s
P = 100W
Energy of a photon,
`E=(hc)/(lamda)=(6.63xx10^(-34)xx3xx10^(-19))/(589xx10^(-9))=3.38xx10^(-19)J`
Number of photons delivered per second `n=(P)/(E)=(100)/(3.38xx10^(-9))=3xx10^(20)`