The energy of the IR photon is [tex]\rm 1.68\;\times\;10^{-21}[/tex] J. Thus, option C is correct.
The energy of the radiations propagating in the air with the velocity of [tex]\rm 3\;\times\;10^8[/tex] m/s is given by:
[tex]E=h\nu[/tex]
Where, h is Planck's constant, and [tex]\nu[/tex] is the frequency.
The value of Planck's constant is given as, [tex]\rm 6.63\;\times\;10^{-34}\;J.s^-^1[/tex]
The frequency of the IR radiation is [tex]\rm 2.53\;\times\;10^1^2\;Hz[/tex]
Substitute the values for the energy of the photon
[tex]\rm E=6.63\;\times\;10^{-34}\;J.s^{-1}\;\times\;2.53\;\times\;10^{12}\;Hz\\ E=16.8\;\times\;10^{-22}\;J\\E=1.68\;\times\;10^{-21}\;J[/tex]
The energy of the IR photon is [tex]\rm 1.68\;\times\;10^{-21}[/tex] J. Thus, option C is correct.
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