Find the wavelength in a hydrogen spectrum between the range `500nm to 700nm`

Options

A. 540nm
B. 580nm
C. 654nm
D. 696nm

Answer

C

Explanation

The energy of a photon wavelength 500nm is `(hc)/(lambda =(1242eV-nm)/(500nm)=2.48eV`
The energy of a photon of wavelength 700nm is
`(hc)/(lambda)=(1242eV-nm)/(700nm)=1.77eV`
The energy difference between the states involved in the transition should, therefore, be between 1.77
eV and `2.44eV.n=3 to n=2` falls in this range
`lambda =(hc)/(Delta E) =(1242eV-nm)/(1.9eV)=654nm` .