The spectral series of the hydrogen spectrum that lies in the ultraviolet region is the

(a) Balmer series                 (b) Pfund series
(c) Paschen series                (d) Lyman series

In terms of Rydberg's constant R, the wave number of the first Balmer line is 
(1) R               

(2) 3R

(3) $\frac{5\mathrm{R}}{36}$         

(4) $\frac{8\mathrm{R}}{9}$

In Bohr's model of hydrogen atom, let PE represents potential energy and TE the total energy. In going to a higher level 

(1) PE decreases, TE increases

(2) PE increases, TE increases

(3) PE decreases, TE decreases

(4) PE increases, TE decreases

An ionic atom equivalent to hydrogen atom has wavelength equal to 1/4 of the wavelengths of hydrogen lines. The ion will be 
(1) ${\mathrm{He}}^{+}$        

(2) ${\mathrm{Li}}^{++}$

(3) ${\mathrm{Ne}}^{9+}$       

(4) ${\mathrm{Na}}^{10+}$

To explain his theory, Bohr used

(a) Conservation of linear momentum

(b) Conservation of angular momentum

(c) Conservation of quantum frequency

(d) Conservation of energy

Hydrogen atoms are excited from ground state of the principal quantum number 4. Then the number of spectral lines observed will be 
(a) 3                   (b) 6
(c) 5                   (d) 2

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. \(81.988~\text{cm}\)

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

Radius of the first orbit of the electron in a hydrogen atom is 0.53 Å. So, the radius of the third orbit will be

(1) 2.12 Å             

(2) 4.77 Å

(3) 1.06 Å             

(4) 1.59 Å