The magnetic moment $\left(\mathrm{\mu }\right)$ of a revolving electron around the nucleus varies with principal quantum number n as

(1) $\mathrm{\mu }\propto \mathrm{n}$            

(2) $\mathrm{\mu }\propto 1/\mathrm{n}$

(3) $\mathrm{\mu }\propto {\mathrm{n}}^2$           

(4) $\mathrm{\mu }\propto 1/{\mathrm{n}}^2$

Bohr's atom model assumes 

(1) The nucleus is of infinite mass and is at rest

(2) Electrons in a quantized orbit will not radiate energy

(3) Mass of electron remains constant

(4) All the above conditions

The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is

1. 1/2                2. 2/137
3. 1/137            4. 1/237

A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for exciting electron from first to third Bohr orbit in ${\mathrm{Li}}^{++}$ will be (Ionisation energy of hydrogen atom is 13.6eV) 
(a) 182.51 Å                 (b) 177.17 Å
(c) 142.25 Å                 (d) 113.74 Å

The ionisation potential of H-atom is  13.6 V. When it is excited from ground state by monochromatic radiations of $970.6 \stackrel{0}{\mathrm{A}}$, the number of emission lines will be (according to Bohr’s theory) 
(1) 10           

(2) 8

(3) 6             

(4) 4

Imagine an atom made up of a proton and a hypothetical particle of double the mass of the electron but having the same charge as the electron. Apply the Bohr atom model and consider all possible transitions of this hypothetical particle to the first excited level. The longest wavelength photon that will be emitted has wavelength $\mathrm{\lambda }$ (given in terms of the Rydberg constant R for the hydrogen atom) equal to

(1) 9/(5R)                 
(2) 36/(5R)
(3) 18/(5R)               
(4) 4/R

In the Bohr model of the hydrogen atom, let R, v and E represent the radius of the orbit, the speed of electron and the total energy of the electron respectively. Which of the following quantity is proportional to the quantum number n ?

(1) R/E               

(2) E/v

(3) RE               

(4) vR

If the atom ${}_{100}{}^{257}\mathrm{Fm}$ follows the Bohr model and the radius of ${}_{100}{}^{257}\mathrm{Fm}$ is n times the Bohr radius, then the value of n is:

(1) 100               
(2) 200
(3) 4                   
(4) $\frac{1}{4}$