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Q. No.Given below are two statements:
| Assertion (A): | The absorption line observed in the spectra of an element is never completely dark. |
| Reason (R): | The sample used for absorption is thin, so that all photons corresponding to a transition may not be absorbed. |
| 1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
| 3. | (A) is true but (R) is false. |
| 4. | Both (A) and (R) are false. |
Subtopic: Spectral Series |
Level 4: Below 35%
Please attempt this question first.
Hints
Please attempt this question first.
Electrons accelerated through a potential difference \(V_0\) are incident on a gas of hydrogen atoms in the ground state. For what minimum value of \(V_0\) will the collisions of the electrons with the atom be perfectly inelastic?
1. \(13.6\) V
2. \(27.2\) V
3. \(10.2\) V
4. \(6.8\) V
1. \(13.6\) V
2. \(27.2\) V
3. \(10.2\) V
4. \(6.8\) V
Subtopic: Bohr's Model of Atom |
Level 4: Below 35%
Hints
Among the given options which is the minimum work function so that light from the Balmer series will not be able to cause any photo-electric effect?
| 1. | \(13.6~\text{eV}\) |
| 2. | \(\dfrac{13.6} {2}~\text{eV}\) |
| 3. | \(13.6×\left(\dfrac{3}{4}\right)~\text{eV}\) |
| 4. | \(13.6×\left(\dfrac14-\dfrac19\right)~\text{eV}\) |
Subtopic: Spectral Series |
Level 4: Below 35%
Hints
A hydrogen atom collides with another similar atom at rest. The minimum energy of the first atom so that one of them may get ionised is:
| 1. | \(13.6\) eV | 2. | \(\dfrac{13.6} {2}\) eV |
| 3. | \(2 \times 13.6\) eV | 4. | \(10.2\) eV |
Subtopic: Bohr's Model of Atom |
Level 4: Below 35%
Hints
A hydrogen atom in the ground state absorbs an ultraviolet photon of wavelength \(25\) nm. Ignore any momentum associated with the photon. The ejected electron has an energy of nearly:
(Take \(hc = 1240\) eV-nm)
1. \(10\) eV
2. \(25\) eV
3. \(35\) eV
4. \(50\) eV
(Take \(hc = 1240\) eV-nm)
1. \(10\) eV
2. \(25\) eV
3. \(35\) eV
4. \(50\) eV
Subtopic: Bohr's Model of Atom |
Level 3: 35%-60%
Hints
For the ground state, the electron in the H-atom has an angular momentum \(\dfrac h{2\pi}\), according to the simple Bohr model. Angular momentum is a vector and hence there will be infinitely many orbits with the vector pointing in all possible directions. In actuality, this is not true,
| 1. | because the Bohr model gives incorrect values of angular momentum. |
| 2. | because only one of these would have a minimum energy. |
| 3. | angular momentum must be in the direction of the spin of the electron. |
| 4. | because electrons go around only in horizontal orbits. |
Subtopic: Bohr's Model of Atom |
Level 3: 35%-60%
Hints
The simple Bohr model cannot be directly applied to calculate the energy levels of an atom with many electrons. This is because:
| 1. | of the electrons not being subjected to a central force. |
| 2. | of the electrons colliding with each other. |
| 3. | of screening effects. |
| 4. | the force between the nucleus and an electron will no longer be given by Coulomb's law. |
Subtopic: Bohr's Model of Atom |
Level 3: 35%-60%
Hints
The zero of the potential energy is so chosen that the total energy of the hydrogen atom in its \(1^{st}\) excited state is zero. Then, the energy of the ground state of the hydrogen atom is:
| 1. | \(-3.4~\text{eV}\) | 2. | \(-6.8~\text{eV}\) |
| 3. | \(-10.2~\text{eV}\) | 4. | \(-13.6~\text{eV}\) |
Subtopic: Bohr's Model of Atom |
Level 3: 35%-60%
Hints
The energy of an atom with a \(K\text-\)shell vacancy is \(E_K\), that with an \(L\text-\)shell vacancy is \(E_L\), and that with an \(M\text-\)shell vacancy is \(E_M\): all compared to an atom with no vacancy, then:
Choose the correct option from the options given below:
| (I) | \(E_K<E_L\) |
| (II) | \(E_L>E_M\) |
| (III) | \(E_L -E_K=E_{K\alpha}\), the energy of \(K_\alpha \) photon |
| 1. | (I) is true | 2. | (I), (III) are true |
| 3. | (II) is true | 4. | (I), (II) are true |
Subtopic: Bohr's Model of Atom |
Level 3: 35%-60%
Hints
The electrostatic potential at the location of an electron in the ground state of the \(\mathrm{H}\)-atom is:
1. \(13.6~\text V\)
2. \(6.8~\text V\)
3. \(27.2~\text V\)
4. \(3.4~\text V\)
1. \(13.6~\text V\)
2. \(6.8~\text V\)
3. \(27.2~\text V\)
4. \(3.4~\text V\)
Subtopic: Bohr's Model of Atom |
Level 3: 35%-60%
Hints
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