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

Orbital acceleration of electrons is:
1. \(\frac{n^2h^2}{4\pi^2m^2r^3}\)
2. \(\frac{n^2h^2}{4n^2r^3}\)
3. \(\frac{4n^2h^2}{\pi^2m^2r^3}\)
4. \(\frac{4n^2h^2}{4\pi^2m^2r^3}\)

Consider the spectral line resulting from transition \(n=2\) to \(n = 1\) in the atoms and ions given below.  The shortest wavelength is given by:

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. ${10}^{-16} m$

Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohr's atomic model:

1. 13.6 eV

2. 0.65 eV

3. 1.9 eV

4. 11.1 eV

As per the Bohr model, the minimum energy (in eV) required to remove the electron from the ground state of a double ionised lithium ion (\(Z=3\)) is:
1. \(1.51\)
2. \(13.6\)
3. \(40.8\)
4. \(122.4\)

The wavelength of K_a X-rays produced by an X-ray tube is 0.76 $\stackrel{\circ }{A}$. Find the atomic number of the anode material of the tube?

1. 41

2. 30

3. 20

4. 10