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

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 

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

(1) 0.3%               

(2) 1%

(3) 31%                 

(4) 3.125%

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

Which of the following is in the increasing order for penetrating power 

(1) $\mathrm{\alpha },\mathrm{\beta },\mathrm{\gamma }$               

(2) $\mathrm{\beta },\mathrm{\alpha },\mathrm{\gamma }$

(3) $\mathrm{\gamma },\mathrm{\alpha },\mathrm{\beta }$               

(4) $\mathrm{\gamma },\mathrm{\beta },\mathrm{\alpha }$

Radioactivity was discovered by

(1) Becquerel           

(2) Pierre Curie

(3) Roentgen             

(4) Rutherford

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

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

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