Advertisements
Advertisements
प्रश्न
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.
पर्याय
b and c
a and c
b and d
c and d
Advertisements
उत्तर
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.
APPEARS IN
संबंधित प्रश्न
Classically, an electron can be in any orbit around the nucleus of an atom. Then what determines the typical atomic size? Why is an atom not, say, a thousand times bigger than its typical size? The question had greatly puzzled Bohr before he arrived at his famous model of the atom that you have learnt in the text. To simulate what he might well have done before his discovery, let us play as follows with the basic constants of nature and see if we can get a quantity with the dimensions of length that is roughly equal to the known size of an atom (~ 10−10 m).
(a) Construct a quantity with the dimensions of length from the fundamental constants e, me, and c. Determine its numerical value.
(b) You will find that the length obtained in (a) is many orders of magnitude smaller than the atomic dimensions. Further, it involves c. But energies of atoms are mostly in non-relativistic domain where c is not expected to play any role. This is what may have suggested Bohr to discard c and look for ‘something else’ to get the right atomic size. Now, the Planck’s constant h had already made its appearance elsewhere. Bohr’s great insight lay in recognising that h, me, and e will yield the right atomic size. Construct a quantity with the dimension of length from h, me, and e and confirm that its numerical value has indeed the correct order of magnitude.
When white radiation is passed through a sample of hydrogen gas at room temperature, absorption lines are observed in Lyman series only. Explain.
In which of the following transitions will the wavelength be minimum?
A hydrogen atom in ground state absorbs 10.2 eV of energy. The orbital angular momentum of the electron is increased by
An electron with kinetic energy 5 eV is incident on a hydrogen atom in its ground state. The collision
Let An be the area enclosed by the nth orbit in a hydrogen atom. The graph of ln (An/A1) against ln(n)
(a) will pass through the origin
(b) will be a straight line with slope 4
(c) will be a monotonically increasing nonlinear curve
(d) will be a circle
Calculate the smallest wavelength of radiation that may be emitted by (a) hydrogen, (b) He+ and (c) Li++.
Find the maximum angular speed of the electron of a hydrogen atom in a stationary orbit.
The average kinetic energy of molecules in a gas at temperature T is 1.5 kT. Find the temperature at which the average kinetic energy of the molecules of hydrogen equals the binding energy of its atoms. Will hydrogen remain in molecular from at this temperature? Take k = 8.62 × 10−5 eV K−1.
Electrons are emitted from an electron gun at almost zero velocity and are accelerated by an electric field E through a distance of 1.0 m. The electrons are now scattered by an atomic hydrogen sample in ground state. What should be the minimum value of E so that red light of wavelength 656.3 nm may be emitted by the hydrogen?
A hydrogen atom moving at speed υ collides with another hydrogen atom kept at rest. Find the minimum value of υ for which one of the atoms may get ionized.
The mass of a hydrogen atom = 1.67 × 10−27 kg.
Consider an excited hydrogen atom in state n moving with a velocity υ(ν<<c). It emits a photon in the direction of its motion and changes its state to a lower state m. Apply momentum and energy conservation principles to calculate the frequency ν of the emitted radiation. Compare this with the frequency ν0 emitted if the atom were at rest.
In a hydrogen atom the electron moves in an orbit of radius 0.5 A° making 10 revolutions per second, the magnetic moment associated with the orbital motion of the electron will be ______.
Let En = `(-1)/(8ε_0^2) (me^4)/(n^2h^2)` be the energy of the nth level of H-atom. If all the H-atoms are in the ground state and radiation of frequency (E2 - E1)/h falls on it ______.
- it will not be absorbed at all.
- some of atoms will move to the first excited state.
- all atoms will be excited to the n = 2 state.
- no atoms will make a transition to the n = 3 state.
What is the process called when an atom absorbs a photon whose energy exactly matches the energy required for an electronic transition?
In what year was Niels Bohr awarded the Nobel Prize in Physics for his explanation of the hydrogen atom spectrum?
When an electron in a rarefied gas atom absorbs a photon, from which energy state to which energy state does the electron transition?
What is a key limitation of continuous spectra that is resolved by the observation of discrete emission lines?
