The ratio of momenta of an electron and an $\mathrm{}$\(\alpha \text-\)particle which are accelerated from rest by a potential difference of \(100~\text{V}\) is:
1. \(1\)
2. \(\sqrt{\frac{2m_e}{m_{\alpha}}}\)
3. \(\sqrt{\frac{m_e}{m_{\alpha}}}\)
4. \(\sqrt{\frac{m_e}{2m_{\alpha}}}\)

The fact that electric charges are integral multiples of the fundamental electronic charge was proved experimentally by 
(1) Planck                   

(2) J.J. Thomson

(3) Einstein                 

(4) Millikan

The specific charge of an electron is 

(a) $1.6\times {10}^{-19}$ coulomb

(b) $4.8\times {10}^{-10}$ stat coulomb

(c) $1.76\times {10}^{11}$ coulomb/kg

(d) $1.76\times {10}^{-11}$  coulomb/kg

The ratio of specific charge of an $\mathrm{\alpha }$-particle to that of a proton is 
(1) 2 : 1                     

(2) 1 : 1

(3) 1 : 2                     

(4) 1 : 3

Which of the following have the highest specific charge

(1) Positron                   

(2) Proton

(3) ${\mathrm{He}}^{++}$                          

(4) None of these

For the Bohr's first orbit of circumference $2\mathrm{\pi r}$, the de-Broglie wavelength of revolving electron will be

(a) $2\mathrm{\pi r}$                       (b) $\mathrm{\pi r}$
(c) $\frac{1}{2\mathrm{\pi r}}$                      (d) $\frac{1}{4\mathrm{\pi r}}$

According to de-Broglie, the de-Broglie wavelength for electron in an orbit of hydrogen atom is ${10}^{-10}$ m. The principle quantum number for this electron is $\left(r=5.13\times {10}^{-11}m\right)$
(a) 1           (b) 2
(c) 3           (d) 4

The energy of a photon of light with wavelength 5000 Å is approximately 2.5 eV. This way the energy of an X-ray photon with wavelength 1Å would be 
(1) 2.5/5000 eV             

(2) $2.5/{\left(5000\right)}^2 \mathrm{eV}$

(3) $2.5\times 5000 \mathrm{eV}$           

(4)  $2.5\times {\left(5000\right)}^2 \mathrm{eV}$

The graph that correctly represents the relation of frequency v of a particular characteristic X-ray with the atomic number Z of the material is

If in nature there may not be an element for which the principal quantum number n > 4, then the total possible number of elements will be

(1) 60                   

(2) 32

(3) 4                     

(4) 64