Question

The Balmer series for the H-atom can be observed ______.

1. if we measure the frequencies of light emitted when an excited atom falls to the ground state.
2. if we measure the frequencies of light emitted due to transitions between excited states and the first excited state.
3. in any transition in a H-atom.
4. as a sequence of frequencies with the higher frequencies getting closely packed.

विकल्प

• b and c

• a and c

• b and d

• c and d

Answer 1

b and d

Explanation:R)

The various lines in the atomic spectra are produced when electrons jump from higher energy state to a lower energy state and photons

• Mainly there are five series and each series is named after its discoverer as Lyman series, Balmer series, Paschen series, Bracket series and Pfund series,
• According to Bohr’s theory, the wavelength of the radiations ‘emitted from hydrogen atom is given by

`1/λ = R[1/n_1^2 - 1/n_2^2]`

⇒ `λ = (n_1^2n_2^2)/((n_1^2 - n_1^2) R) = n_1^2/((1 - n_1^2/n_2^2)R)`

Different spectral series
	Spectral series	Transition	λmax	λmin	`λ_"max"/λ_"min"`	Region
1.	Lyman series	n2 = 2, 3, 4 ... ∞ n1 = 1	`4/(3R)`	`1/R`	`4/3`	Ultraviolet region
2.	Balmer series	n2 = 3, 4, 5 ... ∞ n1 = 2	`36/(5R)`	`4/R`	`9/5`	Visible region
3.	Paschen series	n2 = 4, 5, 6 ... ∞ n1 = 3	`144/(7R)`	`9/R`	`16/7`	Infrared region
4.	Bracket series	n2 = 5, 6, 7 ... ∞ n1 = 4	`400/(9R)`	`16/R`	`25/9`	Infrared region
5.	Pfund series	n2 = 6, 7, 8 ... ∞ n1 = 5	`900/(11R)`	`25/R`	`36/11`	Infrared region

From the above discussion, we can say the Balmer series for the H-atom can be observed if we measure the frequencies of light emitted due to transitions between higher excited states and the first excited state and as a sequence of frequencies with the’higher frequencies getting closely packed.