The ratio of the wavelengths of the last lines of the Balmer and Lyman series is:

1. 4:1

2. 27:5

3. 3:1

4. 9:4

The energy of the emitted photon when an electron in $B{e}^{3+}$ ion returns from n=2 level to the ground state is 

1. 2.616 x 10^-17J

2. 26.16 x 10^-17J

3. 261.6 x 10^-18J

4. 2616 x 10^-17J

The accelerating potential to be imparted to a beam of electrons to give an effective wavelength of 2.42 nm is 

1. 2.56V

2. 3.42V

3. 0.256V

4. 0.342V

The splitting of spectral lines in a magnetic field, arising out of the orbital motion of electrons only and the further splitting due to spin motion are respectively called

1. Zeeman and Stark effects

2. Zeeman and anomalous Zeeman effects

3. Stark and Zeeman effects

4. Zeeman and Kerr effects

A photon of wavelength 300 nm causes the emission of two photons. If the wavelength of one of them is 700 nm. What is the wavelength of the other photon?

1. 525 nm

2. 600 nm

3. 450 nm

4. 300 nm

The electronic transition in the hydrogen atom that emits maximum energy is:

1. 2 $\to$ 1

2. 1 $\to$ 4

3. 4 $\to$ 3

4. 3 $\to$ 2

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