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
If Bohr’s quantisation postulate (angular momentum = nh/2π) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why then do we never speak of quantisation of orbits of planets around the sun?
The first excited energy of a He+ ion is the same as the ground state energy of hydrogen. Is it always true that one of the energies of any hydrogen-like ion will be the same as the ground state energy of a hydrogen atom?
Which wavelengths will be emitted by a sample of atomic hydrogen gas (in ground state) if electrons of energy 12.2 eV collide with the atoms of the gas?
When white radiation is passed through a sample of hydrogen gas at room temperature, absorption lines are observed in Lyman series only. Explain.
The minimum orbital angular momentum of the electron in a hydrogen atom is
Which of the following curves may represent the speed of the electron in a hydrogen atom as a function of trincipal quantum number n?
As one considers orbits with higher values of n in a hydrogen atom, the electric potential energy of the atom
A hydrogen atom in ground state absorbs 10.2 eV of energy. The orbital angular momentum of the electron is increased by
Which of the following products in a hydrogen atom are independent of the principal quantum number n? The symbols have their usual meanings.
(a) vn
(b) Er
(c) En
(d) vr
Ionization energy of a hydrogen-like ion A is greater than that of another hydrogen-like ion B. Let r, u, E and L represent the radius of the orbit, speed of the electron, energy of the atom and orbital angular momentum of the electron respectively. In ground state
Find the binding energy of a hydrogen atom in the state n = 2.
What is the energy of a hydrogen atom in the first excited state if the potential energy is taken to be zero in the ground state?
A gas of hydrogen-like ions is prepared in a particular excited state A. It emits photons having wavelength equal to the wavelength of the first line of the Lyman series together with photons of five other wavelengths. Identify the gas and find the principal quantum number of the state A.
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.
Find the temperature at which the average thermal kinetic energy is equal to the energy needed to take a hydrogen atom from its ground state to n = 3 state. Hydrogen can now emit red light of wavelength 653.1 nm. Because of Maxwellian distribution of speeds, a hydrogen sample emits red light at temperatures much lower than that obtained from this problem. Assume that hydrogen molecules dissociate into atoms.
Average lifetime of a hydrogen atom excited to n = 2 state is 10−8 s. Find the number of revolutions made by the electron on the average before it jumps to the ground state.
Show that the ratio of the magnetic dipole moment to the angular momentum (l = mvr) is a universal constant for hydrogen-like atoms and ions. Find its value.
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?
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 ______.
