The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy?

1. I   

2. II

3. III 

4. IV

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

1. $\frac{k{e}^2}{r^2}$ 

2. $\frac{k{e}^2}{2r}$ 

3. $\frac{k{e}^2}{r}$ 

4. $\frac{k{e}^2}{2r^2}$

What happens whenever a hydrogen atom emits a photon in the Balmer series?

1. it may emit another photon in the Balmer series.

2. it must emit another photon in the Lyman series.

3. it may emit another photon in the Paschen series.

4. it need not emit any more photon.

The ionisation potential of hydrogen atom is

1. 13.60 volt

2. 8.24 volt

3. 10.36 volt 

4. 14.24 bolt

Which source is associated with a line emission spectrum? 

1. Electric fibre 

2. Neon street Sign

3. Red traffic light 

4. Sun

Ionisation potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr's theory, the spectral lines emitted by hydrogen will be:

1. two 

2. three

3. four 

4. one

The frequency of the series limit of the Balmer series of hydrogen atoms in terms of Rydberg constant R and velocity of light C is:

1. $\frac{RC}{4}$

2. RC

3. $\frac{4}{RC}$

4. 4RC

Orbital acceleration of electron is 

1. $\frac{n^2{h}^2}{4{\mathrm{\pi }}^2{\mathrm{m}}^2{\mathrm{r}}^3}$   

2. $\frac{n^2{h}^2}{4n^2{\mathrm{r}}^3}$

3. $\frac{4n^2{h}^2}{{\mathrm{\pi }}^2{\mathrm{m}}^2{\mathrm{r}}^3}$ 

4. $\frac{4n^2{h}^2}{4{\mathrm{\pi }}^2{\mathrm{m}}^2{\mathrm{r}}^3}$

Consider the spectral line resulting from transition n = 2 to n = 1 in the atoms and ions given below.  The shorterst wavelength is given by

1. Hydrogen atom

2. Deuterium

3. Singly ionised helium

4. Doubly ionised lithium

An $\alpha -$particle of energy 5 MeV is scattered through $180°$ by a fixed uranium nucleus. The distance of closest approach is of the order

1. ${10}^{-10} m$ 

2. ${10}^{-13} m$ 

3. ${10}^{-14} m$ 

4. ${10}^{-16} m$