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 

The ratio of minimum to maximum wavelength in Balmer series is 

(1) 5 : 9           

(2) 5 : 36

(3) 1 : 4           

(4) 3 : 4

Rutherford’s $\mathrm{\alpha }$-particle experiment showed that the atoms have

(1) Proton         

(2) Nucleus

(3) Neutron     

(4) Electrons

Which of the following is true for number of spectral lines in going from Lyman series to Pfund series ?

(1) Increases

(2) Decreases

(3) Unchanged

(4) May decreases or increases

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

The first line in the Lyman series has wavelength $\mathrm{\lambda }$. The wavelength of the first line in Balmer series is

(1) $\frac{2}{9}\mathrm{\lambda }$             

(2) $\frac{9}{2}\mathrm{\lambda }$
(3) $\frac{5}{27}\mathrm{\lambda }$           

(4) $\frac{27}{5}\mathrm{\lambda }$

In the following transitions, which one has higher frequency

(1) 3 – 2             

(2) 4 – 3

(3) 4 – 2             

(4) 3 – 1

The diagram depicts the paths of four \(\alpha\)-particles with identical energies being scattered simultaneously by the nucleus of an atom. Which of these paths are/is not physically possible?
                 
1. \((3)\) & \((4)\)
2.  \((2)\) & \((3)\)
3.  \((1)\) & \((4)\)
4. \((4)\) only