A nucleus is bombarded with a high speed neutron so that resulting nucleus is a radioactive one. This phenomenon is called 

(1) Artificial radioactivity         

(2) Fusion

(3) Fission                               

(4) Radioactivity

Which of the following cannot cause fission in a heavy nucleus 

(1) $\mathrm{\alpha }$-particle         

(2) Proton

(3) Deutron             

(4) Laser rays

 If the mass number of an atom is A = 40 and its electron configuration is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^6$, the number of neutrons and protons in its nucleus will be 

(1) 22, 18           

(2) 18, 22

(3) 20, 20           

(4) 18, 18

Which of the following is most unstable

(1) Electrons           

(2) Protons

(3) Neutrons           

(4) $\mathrm{\alpha }$-particle

 Radioactive substance do not emit

(1) Electron           

(2) Helium nucleus

(3) Positron         

(4) Proton

During a negative beta decay 

Some radioactive nucleus may emit

(1) Only one $\mathrm{\alpha },\mathrm{\beta }$ or $\mathrm{\gamma }$ at a time

(2) All the three $\mathrm{\alpha },\mathrm{\beta }$ and $\mathrm{\gamma }$ one after another

(3) All the three $\mathrm{\alpha },\mathrm{\beta }$ and $\mathrm{\gamma }$ simultaneously

(4) Only $\mathrm{\alpha }$ and $\mathrm{\beta }$ simultaneously

Which can pass through 20 cm thickness of the steel

(1) $\mathrm{\alpha }$ particles                   

(2) $\mathrm{\beta }$ particles

(3) $\mathrm{\gamma }$ rays                         

(4) Ultraviolet rays

The half-life period of radium is 1600 years. Its average life time will be 
(a) 3200 years              (b) 4800 years
(c) 2319 years               (d) 4217 years

What percentage of original radioactive atoms is left after five half lives 

(1) 0.3%               

(2) 1%

(3) 31%                 

(4) 3.125%