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Question
Lifetimes of the molecules in the excited states are often measured by using pulsed radiation source of duration nearly in the nanosecond range. If the radiation source has a duration of 2 ns and the number of photons emitted during the pulse source is 2.5 × 1015, calculate the energy of the source.
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Solution
Frequency of radiation (ν),
`"v" = 1/(2.0 xx 10^(9))`
`"v" = 5.0 xx 10^8 " s"^(-1)`
Energy (E) of source = Nhν
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 × 1015) (6.626 × 10–34 Js) (5.0 × 108 s–1)
E = 8.282 × 10–10 J
Hence, the energy of the source (E) is 8.282 × 10–10 J.
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