Assertion (A): | The positively charged nucleus of an atom has a radius of almost 10-15 m. |
Reason (R): | I\(\alpha\)-particle scattering experiment, the distance of the closest approach for \(\alpha\)-particle is ≈10-15 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): | Balmer series lies in the visible region of the electromagnetic spectrum. |
Reason (R): | \(\frac{1}{\lambda}=\mathrm{R}\left[\frac{1}{2^{2}}-\frac{1}{n^{2}}\right], \text { where } n=3,4,5\). |
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 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 H-atom |
c. | the electron's orbit would go around the protons |
d. | the molecule will soon decay in a proton and a H-atom |
1. (a, b)
2. (a, c)
3. (b, c, d)
4. (c, d)