Alpha-Particles Scattering Experiment, Rutherford’s Model Of Atom (Board Level)

1.

In a head-on collision between an a-particle and a gold nucleus, the minimum distance of approach is 3.95 × 10^–14 m. Calculate the energy of the a-particle.

(a) 1MeV

(b) 6MeV

(c) 2MeV

(d) 10MeV

Ans (b)

2.

In an atom, two electrons move around the nucleus in circular orbits of radii R and 4R. The ratio of the time taken by them to complete one revolution is

(a) \frac{1}{4}       

(b) \frac{4}{1}       

(c) \frac{8}{1}       

(d) \frac{1}{8}.

Ans  (d)

3.

The kinetic energy of the electron in an orbit of radius r in hydrogen atom is (e = electronic charge)

(a) \frac{{{{e}^{2}}}}{{{{r}^{2}}}}

(b) \frac{{{{e}^{2}}}}{{2r}}

(c) \frac{{{{e}^{2}}}}{r}                                     

(d) \frac{{{{e}^{2}}}}{{2{{r}^{2}}}}.

Ans (b)

4.

A charged oil drop is suspended in a uniform electric field of 3 × 10⁴ Vm^–1, so that it neither falls nor rises. Find the charge on the drop if its mass is 9.75 × 10^–15kg.

(a) 4.7 × 10^–12 C

(b) 3.8 × 10^–12 C

(c) 3.2 × 10^–12 C

(d) 2.6 × 10^–12 C

Ans (c)

5.

The angular momentum of an electron in a hydrogen atom is proportional to

(a) \frac{1}{{\sqrt{r}}}                                       

(b) \frac{1}{r}       

(c) \sqrt{r}     

(d)r².

Ans (c)

6.

One requires an energy E_n to remove a nucleon from a nucleus and an energy E_e to remove an electron from an atom. Then

(a) {{E}_{n}}={{E}_{e}}                                      

(b) {{E}_{n}}<{{E}_{e}}                                      

(c) {{E}_{n}}>{{E}_{e}}                                      

(d) {{E}_{n}}\ge {{E}_{e}}.

Ans  (c)

7.

Calculate the second excitation potential of single ionized helium.

Given e = 1.6×10^–19 C, m = 9.1  10^–31 kg and h = 6.62  10^–34 J-s.

(a) 6.2 eV

(b) 5.4 eV

(c) 6.9 eV

(d) 7.7 eV

Ans  (a)