Lifetimes of the molecules in the excited states are often measured by using pulsed radiation source of duration nearly in the nano second range. If the radiation source has the duration of `2` ns and the number of photons emitted during the pulse is `2.5xx10^(15)`, calculate the energy of the source.

Explanation

Frequency of radiation (ν),
`v = (1)/(2.0 xx 10^(-9)s)`
`v = 5.0 xx 10^(8) s^(-1)`
Energy (E) of source `= Nhv`
Where,

N = number of photons emitted
h = Planck’s constant
ν = frequency of radiation
Substituting the values in the given expression of (E):
`E = (2.5 xx 10^(15))(6.626 xx 10^(-34)Js)(5.0 xx 10^(8) s^(-1))`
`E = 8.282 xx 10^(-10) J`
Hence, the energy of the source (E) is `8.282 × 10^(-10)` J.