Atoms Physics - Atoms

In 1911, Rutherford, along with his assistants, H. Geiger and E. Marsden, performed the alpha particle scattering experiment. H. Geiger and E. Marsden took radioactive source $(^{214}_{83}\text{Bi})$ for $\alpha$- particles. A collimated beam of $\alpha$-particles of energy 5.5 MeV was allowed to fall on 2.1 × 10^-7 m thick gold foil. The $\alpha$-particles were observed through a rotatable detector consisting of a Zinc sulphide screen and microscope. It was found that CL-particles got scattered. These scattered $\alpha$-particles produced scintillations on the zinc sulphide screen. Observations of this experiment are as follows?

Most of the $\alpha$-particles passed through the foil without deflection.

Only about 0.14% of the incident $\alpha$-particles scattered by more than 1º

Only about one $\alpha$-particle in every 8000 $\alpha$-particles deflected by more than 90º

These observations led to many arguments and conclusions which laid down the structure of the nuclear model of an atom.

1. Rutherford's atomic model can be visualised as.

2. Gold foil used in Geiger-Marsden experiment is about 10^-8 m thick. This ensures.

1. Gold foil's gravitational pull is small or possible.
2. Gold foil is deflected when $\alpha$-particle stream is not incident centrally over it.
3. Gold foil provides no resistance to passage of $\alpha$-particles.
4. Most $\alpha$-particle will not suffer more than 1º scattering during passage through gold foil.

3. In Geiger-Marsden scattering experiment, the trajectory traced by an $\alpha$-particle depends on.

1. Number of collision.
2. Number of scattered $\alpha$- particles.
3. Impact parameter.
4. None of these.

4. In the Geiger-Marsden scattering experiment, in case of head-on collision, the impact parameter should be.

1. Maximum
2. Minimum
3. Infinite
4. zero

5. The fact only a small fraction of the number of incident particles rebound back in Rutherford scattering indicates that.

1. Number of $\alpha$-particles undergoing head-on-collision is small.
2. Mass of the atom is concentrated in a small volume.
3. Mass of the atom is concentrated in a large volume.
4. Both (a) and (b).

At room temperature, most of the H-atoms are in ground state. When an atom receives some energy (i.e., by electron collisions), the atom may acquire sufficient energy to raise electron to higher energy state. In this condition, the atom is said to be in excited state. From the excited state, the electron can fall back to a state of lower energy emitting a photon equal to the energy difference of the orbit.

In a mixture of He-He gas (He⁺ is singleionized He atom). H-atoms and He⁺ ions are excited to their respective first excited states. Subsequently, H-atoms transfer their total excitation energy to He⁺ ions (by collisions)

1. The quantum number n of the state finally populated in He⁺ ions is.

1. 2
2. 3
3. 4
4. 5

2. The wavelength of light emitted in the visible region by He⁺ ions after collisions with H-atoms is.

1. 6.5 × 10^-7 m
2. 5.6 × 10^-7 m
3. 4.8 × 10^-7 m
4. 4.0 × 10^-7 m

3. The ratio of kinetic energy of the electrons for the H-atoms to that of He⁺ ion for n = 2 is.

1. $\frac{1}{4}$

2. $\frac{1}{2}$

3. 1
4. 2

4. The radius of the ground state orbit of H-atoms is.

1. $\frac{\in_0}{\text{h}\pi\text{me}^2}$

2. $\frac{\text{h}^2\in_0}{\pi\text{me}^2}$

3. $\frac{\pi\text{me}^2}{\text{h}}$

4. $\frac{2\pi\text{h}\in_0}{\text{me}^2}$

5. Angular momentum of an electron in H-atom in first excited state is.

1. $\frac{\text{h}}{\pi}$

2. $\frac{\text{h}}{2\pi}$

3. $\frac{2\pi}{\text{h}}$

4. $\frac{\pi}{\text{h}}$