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

Alpha rays emitted from a radioactive substance are

(1) Negatively charged particles

(2) Ionised hydrogen nuclei

(3) Doubly ionised helium atom

(4) Uncharged particles having the mass equal to proton

Half life of ${\mathrm{Bi}}^{210}$ is 5 days. If we start with 50,000
atoms of this isotope, the number of atoms left over after 10
days is 

(1) 5,000               

(2) 25,000

(3) 12,500             

(4) 20,000

A nucleus of atomic mass A and atomic number Z emits $\mathrm{\beta }$-particles. The atomic mass and atomic number of the resulting nucleus are 

(1) A, Z             

(2) A + 1, Z

(3) A, Z + 1       

(4) A-4, Z-2 

Radioactivity was discovered by

(1) Becquerel           

(2) Pierre Curie

(3) Roentgen             

(4) Rutherford

The average life T and the decay constant $\mathrm{\lambda }$ of a radioactive nucleus are related as 

(1) $\mathrm{T\lambda }=1$               

(2) $\mathrm{T}=\frac{0.693}{\mathrm{\lambda }}$

(3) $\frac{\mathrm{T}}{\mathrm{\lambda }}=1$               

(4) $\mathrm{T}=\frac{\mathrm{c}}{\mathrm{\lambda }}$

If T is the half life of a radioactive material, then the fraction that would remain after a time $\frac{\mathrm{T}}{2}$ is 
(1) $\frac{1}{2}$             

(2) $\frac{3}{4}$
(3) $\frac{1}{\sqrt{2}}$           

(4) $\frac{\sqrt{2}-1}{\sqrt{2}}$