When an electron in hydrogen atom is excited, from its 4th to 5th stationary orbit, the change in angular momentum of electron is (Planck’s constant: h = $6.6\times {10}^{-34} \mathrm{J}-\mathrm{s}$6.6)

(1) $4.16\times {10}^{-34} \mathrm{J}-\mathrm{s}$              

(2) $3.32\times {10}^{-34 }\mathrm{J}-\mathrm{s}$

(3) $1.05\times {10}^{-34} \mathrm{J}-\mathrm{s}$               

(4) $2.08\times {10}^{-34} \mathrm{J}-\mathrm{s}$

The concept of stationary orbits was proposed by

(1) Neil Bohr             

(2) J.J. Thomson

(3) Ruther ford           

(4) I. Newton

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