Electron are emited from an electron gun at almost zero velocity and are accelerated by an electric field E through a distance of `1.0m` The electron are now scatteared by an atomic hydrogen sample in ground state what should be the minimum value of E so that red light of wavelength `656.5 nm` may be emitted by the hydrogen?

Answer

A, B

Explanation

The given wavelength in Balmer series. The first line, which requires minium energy is from
`n_1=3` to `n_2 =2`
:. The energy should be equal to the energy required for tansition from ground state to `n=3`
i.e. `E=13.6(1-(1)/(9))`
`=(13.6 xx 8)/(9) =12.09 eV`.
:. Minimum value of electric field
`=12.09 V//m`
`=12.1 V//m`