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

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

The half life of a radioactive element which has only $\frac{1}{32}$ of its original mass left after a lapse of 60 days is

(1) 12 days                 

(2) 32 days

(3) 60 days                 

(4) 64 days

The half-life of ${\mathrm{Bi}}^{210}$ is 5 days. What time is taken by (7/8)th part of the sample to decay 

(1) 3.4 days               

(2) 10 days

(3) 15 days               

(4) 20 days