Question

Which of the following series of transitions in the spectrum of hydrogen atom falls in visible region?

• A. Lyman series
• B. Balmer series
• C. Paschen series
• D. Brackett series

Answer 1

The correct option is B Balmer series

The wavelength of visible light ranges from 380 nm to 780 nm. Only the wavelengths of these ranges can be seen by the human eye.
Electrons jump from higher energy level to lower energy level releasing energy in form of spectral emissions. The spectral lines are grouped together to form the spectral series. Hydrogen shows 4 such series named Lyman, Balmer, Brackett and Paschen.
The energy differences and the wavelengths of the emitted photons is related by Rydberg formula as:
$\frac{1}{\lambda }=Z^{2}R(\frac{1}{n_1^2}-\frac{1}{n_1^2})$
Where Z is the atomic number, n is the principal quantum number and the numbers 1 and 2 represent the lower and higher energy levels and R is the Rydberg’s constant.
Different series are obtained by changing the values of n as 1,2,3 and 4 for hydrogen. The value of R for hydrogen is $1.09677\times {10}^7{m}^{-1}$
Putting the values of R and Z, we can find the values of the wavelengths for different values of the energy levels and by doing so, it is observed that the range of wavelengths for visible light is obtained in the Balmer series only.
-The range for Lyman series starts from 121 nm and decreases further, Balmer series starts from 656 nm, Paschen series starts from 1875 nm and Brackett series starts from 4051 nm.
Therefore it can be concluded that Balmer series falls under the visible region in the hydrogen spectrum and the correct option is B