Question

$$_{87}^{221}Ra$$  is a radioactive substance having half life of 4 days. Find the probability that a nucleus undergoes decay after two half lives

A. 1
B. $$\frac{1}{2}$$
C. $$\frac{3}{4}$$  
D. $$\frac{1}{4}$$
Answer :   $$\frac{3}{4}$$
Solution :
For a nucleus to disintegrate in two half life, the probability is $$\frac{3}{4}$$ as $$75\% $$ of the nuclei will disintegrate in this time.

Releted MCQ Question on
Modern Physics >> Radioactivity

Releted Question 1

An alpha particle of energy $$5\,MeV$$  is scattered through $${180^ \circ }$$ by a fixed uranium nucleus. The distance of closest approach is of the order of

A. $$1\, \mathop {\text{A}}\limits^ \circ $$
B. $${10^{ - 10}}cm$$
C. $${10^{ - 12}}cm$$
D. $${10^{ - 15}}cm$$
Releted Question 2

Beta rays emitted by a radioactive material are

A. electromagnetic radiations
B. the electrons orbiting around the nucleus
C. charged particles emitted by the nucleus
D. neutral particles
Releted Question 3

Consider $$\alpha $$ particles, $$\beta $$ particles and $$\gamma $$ - rays, each having an energy of $$0.5\,MeV.$$  In increasing order of penetrating powers, the radiations are:

A. $$\alpha ,\beta ,\gamma $$
B. $$\alpha ,\gamma ,\beta $$
C. $$\beta ,\gamma ,\alpha $$
D. $$\gamma ,\beta ,\alpha $$
Releted Question 4

A radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains is

A. 1080
B. 2430
C. 3240
D. 4860

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