Question

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 source is 2.5 × 1015, calculate the energy of the source.

Answer 1

Answer:

Number of emitted photons =2.5×10

15

Formulas to be used:

Energy =Nhω

Where N = number of emitted photons during the pulse source

h= Planck’s constant =6.626×10

−34

ω=frequencyoftheradiationsource

Frequency of source=

Durationofthesource

1

Calculation:

Step 1: Find frequency of source

Durationofthesource

1

2×10

−9

1

=0.5×10

9

Step 2: Substituting

N=2.5×10

15

h=6.626×10

−34

ω=0.5×10

9

In the energy formula, we get ,

Energy =(2.5×10

15

)(6.626×10

−34

)(0.5×10

9

)=8.28×10

−10

J