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Question
The Balmer series for the H-atom can be observed ______.
- if we measure the frequencies of light emitted when an excited atom falls to the ground state.
- if we measure the frequencies of light emitted due to transitions between excited states and the first excited state.
- in any transition in a H-atom.
- as a sequence of frequencies with the higher frequencies getting closely packed.
Options
b and c
a and c
b and d
c and d
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Solution
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.
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