• # question_answer The energy of a photon of light with wavelength 5000 $\overset{\text{o}}{\mathop{\text{A}}}\,$ is approximately 2.5 eV. This way the energy of an X-ray photon with wavelength 1$\overset{\text{o}}{\mathop{\text{A}}}\,$ would be A)  2.5/5000 eV B) $2.5/{{(5000)}^{2}}eV$ C) $2.5\times 5000\ eV$      D) $2.5\times {{(5000)}^{2}}eV$

[c] $E\propto \frac{1}{\lambda }\Rightarrow \frac{2.5}{E'}=\frac{1}{5000}\Rightarrow E'=(2.5)\times 5000\ eV$