The spectrum of He-atom may be considered similar to the spectrum of - 

1. H

2. Li⁺

3. Na

4. He⁺

The frequency ratio between violet (400nm) and red (750nm) radiations in the visible spectrum, is-

1. 8/15

2. 4/15

3. 15/8

4. None of these

The Compton wavelength for an electron is  $\left(\frac{h}{m_{0}c}\right)$

0.024 Å 

calculate $∆\lambda$= $\left(\frac{h}{m_{0}c}\right)$(1- cos θ) for a scattering angle  θ = $\mathrm{\pi }$/3. What is the maximum value for $∆\lambda$ ?

1. 0.024 Å, 0.048 Å

2. 0.012 Å, 0.048 Å

3. 0.012 Å, 0.024 Å

4. 0.006 Å, 0.012 Å

Positronium is an unstable complex of electron and positron, both of the same mass, but opposite charge. Apply Bohr's theory of hydrogen atom to this system and obtain the energy required to separate the electron from the positron.

(ionization energy of the ground state hydrogen atom= 13.62eV.) Express the result in KJmol^-1

1. 550 KJmol^-1

2. 657 KJmol^-1

3. 851 KJmol^-1

4. 720 KJmol^-1

The total spin resulting for a 3d⁷ configuration is 

1. 3/2

2. 1/2

3. 2

4. 1

Supposing the energy of the fourth shell for the hydrogen atom is -50a.u. (Arbitrary unit). What would be its ionization potential-

1. 50

2. 800

3. 15.4

4. 20.8

An element with atomic mass Z consists of two isotopes of mass number Z-1 and Z + 2. The percentage abundance of the heavier isotope is -

1. 0.25

2. 33.3

3. 66.6

4. 75

Two isotopes of Boron are found in the nature with atomic weights 10.01(I) and 11.01(II). The atomic weight of natural Boron is 10.81. The percentage of (I) and (II) isotopes in it are respectively-

1. 20 and 80

2. 10 and 90

3. 15 and 75

4. 30 and 70

Calculate the wavenumber of lines having the frequency of 5 x 10¹⁶ cycles per sec. 

1. 1.666 x 10⁸m^-1 

2. 0.666 x 10⁸m^-1

3. 4.126 x 10⁶m^-1

4. 3.133 x 10⁴m^-1

Which of the following set of quantum number is not valid

1. n = 1 , $\mathcal{l}$ = 2

2. n=2, m = 1

3. n =3, $\mathcal{l}$ = 0

4. n = 4, $\mathcal{l}$ = 2