The wavelength of the photon is:
[tex]\lambda =12.0 cm=0.12 m[/tex]
We can find its frequency by using the relationship:
[tex]f= \frac{c}{\lambda} [/tex]
where c is the speed of light. Substituting the wavelength into the formula, we find
[tex]f= \frac{c}{\lambda}= \frac{3 \cdot 10^8 m/s}{0.12 m}=2.5 \cdot 10^9 Hz [/tex]
and now we can calculate the energy of the photon by using:
[tex]E=hf=(6.6\cdot 10^{-34} Js)(2.5 \cdot 10^9 Hz)=1.65 \cdot 10^{-24} J[/tex]
