If a source of power 8 kW producees `10^(22)` photons/ second, the wavelength of the radiation is

Options

A. `1*5xx10^(-6) m`
B. `2*5xx10^(-7) m`
C. `1.4xx10^(-3)m`
D. `1.2xx10^(-5)m`

Answer

B

Explanation

Power of the source =8 kW
`=8xx10^(-3) W`
But power `=("Work")/(T)=("Energy")/("Time")`
But E = hv and for n photons,
`E=hv`
`:. P=(nhv)/(t)=nHv`
where `N=(n)/(t)` number of photons emitted per sec
`:. P=(Nhc)/(lambda)( :. v=(c)/(lambda))`
`:. lambda=(Nhc)/(P)`
`=(10^(22)xx6.63xx10^(34)xx3xx10^(8))/(8xx10^(3))`
`=2.5xx10^(-7)m`