Assertion (A): | The positively charged nucleus of an atom has a radius of almost \(10^{-15}~\text{m}\). |
Reason (R): | I\(\alpha\)-particle scattering experiment, the distance of the closest approach for \(\alpha\)-particle is \(\approx 10^{-15}~\text m\). | n
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. |
Assertion (A): | The hydrogen atom consists of only one electron but its emission spectrum has many lines. |
Reason (R): | Only Lyman series is found in the absorption spectrum of hydrogen atoms whereas in the emission spectrum, all the series are found. |
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. |
Assertion (A): | The Balmer series lies in the visible region of the electromagnetic spectrum. |
Reason (R): | \(\frac{1}{\lambda}={R}\left[\frac{1}{2^{2}}-\frac{1}{n^{2}}\right], \text { where } n=3,4,5.\) |
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. | (A) is False but (R) is True. |
Assertion (A): | Rydberg's constant does not vary with the mass number of a given element. |
Reason (R): | The reduced mass of the electron is dependent on the mass of the nucleus only. |
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. |
Assertion (A): | LASER is used to measure distant objects as moon. |
Reason (R): | They are highly coherent sources of light. |
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. |
Assertion (A): | Bohr had to postulate that the electrons in stationary orbits around the nucleus do not radiate. |
Reason (R): | According to classical physics all accelerating electrons radiate. |
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. |
Assertion (A): | In He-Ne laser, population inversion takes place between energy levels of neon atoms. |
Reason (R): | Helium atoms have a meta-stable energy level. |
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. |
Assertion (A): | A hydrogen atom at the ground state cannot absorb a photon of energy 10 eV. |
Reason (R): | First excitation energy of the hydrogen atom is 10.2 eV. The hydrogen atom absorbs only those photons which provide it the excitation energy. |
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. |
Assertion (A): | Magnetic moment associated with an electron in hydrogen atom is quantized. |
Reason (R): | Magnetic moment associated with the electron is an integral multiple of Bohr's magneton but is independent of atomic number. |
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. |
An ionised \(\text H\)-molecule consists of an electron and two protons. The protons are separated by a small distance of the order of angstrom. In the ground state:
(a) | the electron would not move in circular orbits. |
(b) | the energy would be \(2^{4}\) times that of a \(\text H\)-atom. |
(c) | the electron's orbit would go around the protons. |
(d) | the molecule will soon decay in a proton and a \(\text H\)-atom. |
1. | (a), (b) | 2. | (a), (c) |
3. | (b), (c), (d) | 4. | (c), (d) |