The wavelength of the energy emitted when electrons come from the fourth orbit to the second orbit in hydrogen is \(20.397~\text{cm}\). The wavelength of energy for the same transition in \(\mathrm{He^{+}}\) is:
1. \(5.099~\text{cm}\)
2. \(20.497~\text{cm}\)
3. \(40.994~\text{cm}\)
4. \(81.988~\text{cm}\)

Minimum excitation potential of Bohr's first orbit in hydrogen atom is
(1) 13.6 V                     

(2) 3.4 V

(3) 10.2 V                     

(4) 3.6 V

Which of the following statements are true regarding Bohr's model of hydrogen atom?

(I) Orbiting speed of electron decreases as it shifts to discrete orbits away from the nucleus

(II) Radii of allowed orbits of electron are proportional to  principal quantum number

(III) Frequency with which electrons orbits around the nucleus in discrete orbits is inversely proportional to the cube of principal quantum number

(IV) Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits
Select correct answer using the codes given below
Codes :
(1) I and III                 

(2) II and IV

(3) I, II and III           

(4) II, III and IV

 For electron moving in ${\mathrm{n}}^{\mathrm{th}}$ orbit of H-atom the angular velocity is proportional to 
(1) n                       

(2) 1/n

(3) ${\mathrm{n}}^3$                    

(4) 1/${\mathrm{n}}^3$

Which of the following spectral series in hydrogen atom give spectral line of 4860 Å 

(1) Lyman               

(2) Balmer

(3) Paschen             

(4) Brackett

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${\mathrm{r}}_0$