A narrow electron beam passes undeviated through an electric field E = $3\times {10}^4 \mathrm{volt}/\mathrm{m}$ and an overlapping magnetic field $\mathrm{B}=2\times {10}^{-3} \mathrm{Weber}/{\mathrm{m}}^2$. If electric field and magnetic field are mutually perpendicular. The speed of the electrons is 
1. \(60\) m/s                       
2. $10.3\times {10}^7 \mathrm{m}/\mathrm{s}$
3. $1.5\times {10}^7 \mathrm{m}/\mathrm{s}$             
4. $0.67\times {10}^{-7 }\mathrm{m}/\mathrm{s}$

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

Cathode rays are similar to visible light rays in that

(1) They both can be deflected by electric and magnetic fields

(2) They both have a definite magnitude of wavelength

(3) They both can ionize a gas through which they pass

(4) They both can expose a photographic plate

A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength $20 {\mathrm{Vm}}^{-1}$ and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons

1. 20 ${\mathrm{ms}}^{-1}$                  2. 40 ${\mathrm{ms}}^{-1}$ 
3. 8 ${\mathrm{ms}}^{-1}$                    4. 5.5 ${\mathrm{ms}}^{-1}$

Electron volt is a unit of 
(1) Potential                         

(2) Charge

(3) Power                             

(4) Energy

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

In Bainbridge mass spectrograph a potential difference of 1000 V is applied between two plates distant 1 cm apart and magnetic field in B = 1T. The velocity of undeflected positive ions in m/s from the velocity selector is

(1)${10}^7 \mathrm{m}/\mathrm{s}$                    

(2) ${10}^4 \mathrm{m}/\mathrm{s}$

(3) ${10}^5 \mathrm{m}/\mathrm{s}$                   

(4) ${10}^2 \mathrm{m}/\mathrm{s}$ 

Order of q/m ratio of proton, $\alpha$-particle and electron is

(a) $\mathrm{e}>\mathrm{p}>\mathrm{\alpha }$               (b) $\mathrm{p}>\mathrm{\alpha }>\mathrm{e}$

(c) $\mathrm{e}>\mathrm{\alpha }>\mathrm{p}$               (d) None of these

${\mathrm{O}}^{++}, {\mathrm{C}}^{+}, {\mathrm{He}}^{++}$ and ${\mathrm{H}}^{+}$ ions are projected on the photographic plate with the same velocity in a mass spectrograph. Which one will strike the farthest?
1. ${\mathrm{O}}^{++}$
2. ${\mathrm{C}}^{+}$
3. ${\mathrm{He}}^{++}$
4. H⁺

In an electron gun, the electrons are accelerated by the potential V. If e is the charge and m is the mass of an electron, then the maximum velocity of these electrons will be

(1) $\frac{2\mathrm{eV}}{\mathrm{m}}$                   

(2) $\sqrt{\frac{2\mathrm{eV}}{\mathrm{m}}}$

(3) $\sqrt{\frac{2\mathrm{m}}{\mathrm{eV}}}$                 

(4) $\frac{{\mathrm{V}}^2}{2\mathrm{em}}$