Radioactivity is

(1) Irreversible process             

(2) Self disintegration process

(3) Spontaneous process           

(4) All of the above

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

Atomic mass number of an element thorium is 232 and its atomic number is 90. The end product of this radioactive element is an isotope of lead (atomic mass 208 and atomic number 82). The number of alpha and beta particles emitted is

 
(1) $\mathrm{\alpha }$=3, $\mathrm{\beta }$ = 3       

(2) $\mathrm{\alpha }$ = 6, $\mathrm{\beta }$ = 4

(3) $\mathrm{\alpha }$=6, $\mathrm{\beta }$=0         

(4) $\mathrm{\alpha }$=4, $\mathrm{\beta }$=6

The decay constant of radium is $4.28\times {10}^{-4}$ per year. Its half life will be 

(1) 2000 years       

(2) 1240 years

(3) 63 years           

(4) 1620 years

A sample contains 16 gm of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is

(1) Less than 1 mg         

(2) $\frac{1}{4}\mathrm{gm}$ 

(3) $\frac{1}{2}\mathrm{gm}$                       

(4) 1 gm

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

Half life of radioactive element depends upon

(1) Amount of element present 

(2) Temperature

(3) Pressure

(4) Nature of element

Which of the following is not a mode of radioactive decay

(1) Positron emission           

(2) Electron capture

(3) Fusion                         

(4) Alpha decay