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. |
1. | \(13.6~\text{eV}\) |
2. | \(\dfrac{13.6} {2}~\text{eV}\) |
3. | \(13.6×\left(\dfrac{3}{4}\right)~\text{eV}\) |
4. | \(13.6×\left(\dfrac14-\dfrac19\right)~\text{eV}\) |
1. | \(13.6\) eV | 2. | \(\dfrac{13.6} {2}\) eV |
3. | \(2 \times 13.6\) eV | 4. | \(10.2\) eV |
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. |
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. |
1. | \(-3.4~\text{eV}\) | 2. | \(-6.8~\text{eV}\) |
3. | \(-10.2~\text{eV}\) | 4. | \(-13.6~\text{eV}\) |
(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 |