Question

Longest wavelength in Balmer series of He+1 is

Answer 1

See longest wavelength line of any series in hydrogen spectrum is the first line of the series.Again 1/ R = 912 Angstrom where R= Rydberg constant.1/ wavelength = R z^2 { 1/ n1^2 - 1/ n2^2 }n1= 2 and n2 = 3 as it is balmer series.

Answer 2

The longest wavelength in the Balmer series of He+1 is  $656.3nm$

Explanation:

• The wavelength of a photon emitted due to transition in H-atom

       ⇒  $\frac{1}{lamda L} =R(\frac{1}{n1^{2} } -\frac{1}{n2^{2} })$

• The longest wavelength is emitted in the Balmer series if the transition of electron takes place from n2 =3 to n1 =2

• Longest wavelength in Balmer series  $\frac{1}{lamda L} =R(\frac{1}{2^{2} } -\frac{1}{3^{2} })$

        ⇒ $\frac{1}{lamda L} =\frac{36}{5R}$   Given $R=1.097$×$10^{7}m^{-1}$

• On substituting the value of R we get wavelengths of the Balmer series of hydrogen atoms as $656.3nm$

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