Which of the following is most unstable

(1) Electrons           

(2) Protons

(3) Neutrons           

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

In the reaction ${}_1{}^2\mathrm{H}+{}_1{}^3\mathrm{H}\to {}_2{}^4\mathrm{He}+{}_0{}^1\mathrm{n}$. If the tending energies of ${}_1{}^2\mathrm{H},{}_1{}^3\mathrm{H}$ and ${}_2{}^4\mathrm{He}$ are respectively a,b and c (in MeV), then the energy (in MeV) released in this reaction is

(1) c+a-b           

(2) c-a-b

(3) a+b+c         

(4) a+b-c 

Fission of nuclei is possible because the binding energy per nucleon in them:

 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%

Beta rays emitted by a radioactive material are

(1) Electromagnetic radiation

(2) The electrons orbiting around the nucleus

(3) Charged particles emitted by nucleus

(4) Neutral particles