Answer:
[tex]1.64\cdot 10^{-24}J[/tex]
Explanation:
The energy of a photon is given by:
[tex]E=\frac{hc}{\lambda}[/tex]
where
[tex]h=6.63\cdot 10^{-34} Js[/tex] is the Planck constant
[tex]c=3\cdot 10^8 m/s[/tex] is the speed of light
[tex]\lambda[/tex] is the wavelenght of the photon
For the microwave photons in this problem,
[tex]\lambda=12.1 cm=0.121 m[/tex]
so their energy is
[tex]E=\frac{(6.63\cdot 10^{-34}Js)(3\cdot 10^8 m/s)}{0.121 m}=1.64\cdot 10^{-24}J[/tex]
