question_answer 68)

Lifetimes of the molecules in the excited state are often measured by using a pulse radiation source of duration nearly in nano second range. If the radiation source has the duration of 2 ns and the number of photons emitted during the pulse source is \[2.5\times {{10}^{15}}\], calculate the energy of the source.

Answer:

Time period T = \[2\times {{10}^{-9}}s\] Frequency \[v=\frac{1}{T}=\frac{1}{2\times {{10}^{-9}}}=5\times {{10}^{8}}{{s}^{-1}}\] Energy = \[x\,h\,v\] \[=2.5\times {{10}^{15}}\times 6.6\times {{10}^{-34}}\times 5\times {{10}^{8}}\text{J}\] \[=8.25\times {{10}^{-10}}J\]