Electrons having kinetic energy 30 e V are made to collide with atomic hydrogen gas (in ground state) and 42 . 5 % of electron energy is used to excite the hydrogen atoms. The number of emitted wavelengths in emission spectra are

Step-by-step solution

42 . 5 % of 30 e V = 12.75 e V ∴ E 4 - E 1 = - 0.85 - - 13.6 = 12.75 e V So, it means electron has been transmitted from ground state to 3 r d excited state n = 4 , so total number of unique wavelengths emitted are = 4 × 4 - 1 2 = 6