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)` ?

Options

A. `lambda = (h c)/(E_(1) + E_(2))`
B. `lambda = (2 h c)/(E_(1) + E_(2))`
C. `lambda = (2 h c)/(E_(1) - E_(2))`
D. `lambda = (h c)/(E_(1) - E_(2))`

Answer

D

Explanation

By quantum thoery of radiation, the energy change `delta E` between energy level is proportional to the frequency of electromagnetic radiation `f` and is given by.
`Delta E = h f = (h c)/)lambda)`
`Hence, `lambda = (h c)/(Delta E) = (h c)/(E_(1) - E_(2))`