The velocity of the electron in the ground state (H - atom) is 

1. $2.18\times {10}^5 m/s$   

2. $2.18\times {10}^6 m/s$

3. $2.18\times {10}^7 m/s$   

4. $2.18\times {10}^8 m/s$

The element which has K$\alpha$ X-ray line whose wavelength is 0.18 nm is:

1. Cobalt 

2.  Xenon

3. Copper 

4. Iron

Calculate the highest frequency of the emitted photon in the Paschen series of spectral lines of the Hydrogen atom:

1. $3.7\times {10}^{14} Hz$ 

2. $9.1\times {10}^{15} Hz$

3. $10.23\times {10}^{14} Hz$

4. $29.7\times {10}^{15} Hz$

Which of the following transitions gives photon of maximum energy?

1. n = 1 to n = 2 

2. n = 2 to n = 1

3. n = 2 to n = 6 

4. n = 6 to n = 2

Hydrogen atoms are excited from ground state of the principal quantum number 4. Then, the number of spectral lines observed will be

1. 3   

2. 6

3. 5

4. 2

When electron jumps from n = 4 to n = 2 orbit, we get [2000]

1. second line of Lyman series

2. second line of Balmer series

3. second line of Paschen series

4. an absorption line of Balmer series

The spectrum obtained from a sodium vapour lamp is an example of

1. band spectrum

2.  continuous spectrum

3. emission spectrum

4. absorption spectrum

In terms of Bohr radius $a_0$, the radius of the second Bohr orbit of a hydrogen atom is given by [1992]

1. 4$a_0$ 

2. 8$a_0$ 

3. $\sqrt{2}$$a_0$     

4. 2$a_0$