Line spectra (J86/I/28)

Answer is C.


Transition from E4 to E2 gives a photon with wavelength corresponding to blue wavelength. Visible wavelength involves transition from higher energy level to E2 (Balmer series).

Line spectra of Hydrogen

For a red wavelength photon, the energy is less than that of a blue photon. Transition required is therefore from E3 to E2.