Question

An atom emits a spectral line of wavelength $\lambda$ when an electron makes a transition between levels of energy $E_1$ and $E_2$. Which expression correctly relates $\lambda ,E_1$ and $E_2$?

• A. $\lambda =\frac{hc}{E_1+E_2}$
• B. $\lambda =\frac{2hc}{E_1+E_2}$
• C. $\lambda =\frac{2hc}{E_1-E_2}$
• D. $\lambda =\frac{hc}{E_1-E_2}$

Answer 1

The correct option is D $\lambda =\frac{hc}{E_1-E_2}$

Energy difference between the two states, is transformed into a photon.
Then the given equation to use is:
$E_1-E_2=\frac{hc}{\lambda }$
$\lambda =\frac{hc}{E_1-E_2}$