Who discovered spin quantum number 

(1) Unlenbeck and Goudsmit

(2) Nell’s Bohr

(3) Zeeman

(4) Sommerfield

The time of revolution of an electron around a nucleus of charge Ze in nth Bohr orbit is directly proportional to

(1) n             

(2) $\frac{{\mathrm{n}}^3}{{\mathrm{Z}}^2}$

(3) $\frac{{\mathrm{n}}^2}{\mathrm{Z}}$         

(4) $\frac{\mathrm{Z}}{\mathrm{n}}$

In Bohr’s model, if the atomic radius of the first orbit is ${\mathrm{r}}_0$, then the radius of the fourth orbit is 
(1) ${\mathrm{r}}_0$             

(2) 4${\mathrm{r}}_0$

(3)${\mathrm{r}}_0$/16         

(4) 16${\mathrm{r}}_0$

If R is the Rydberg’s constant for hydrogen the wave number of the first line in the Lyman series will be

(1) $\frac{\mathrm{R}}{4}$                   

(2) $\frac{3\mathrm{R}}{4}$
(3) $\frac{\mathrm{R}}{2}$                 

(4) 2R

In hydrogen atom, if the difference in the energy of the electron in n =2 and n = 3 orbits is E, the ionization energy of hydrogen atom is 

(1) 13.2 E               

(2) 7.2 E

(3) 5.6 E                 

(4) 3.2 E

The first member of the Paschen series in hydrogen spectrum is of wavelength 18,800 Å. The short wavelengths limit of Paschen series is 

(1) 1215 Å     

(2) 6560 Å

(3) 8225 Å     

(4) 12850 Å

In Bohr model of hydrogen atom, the ratio of periods of revolution of an electron in n =2 and n = 1 orbits is

(1) 2 : 1             

(2) 4 : 1

(3) 8 : 1             

(4) 16 : 1

The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true