What happens to the mass number and the atomic number of an element when it emits \(\gamma\text{-}\)radiation?

1.	mass number decreases by four and atomic number decreases by two.
2.	mass number and atomic number remain unchanged.
3.	mass number remains unchanged while the atomic number decreases by one.
4.	mass number increases by four and the atomic number increases by two.

The half-life of a radioactive sample undergoing \(\alpha- \text{decay}\) is $1.4\times {10}^{17}$ $\sec$. If the number of nuclei in the sample is $2.0$ $\times$ ${10}^{21}$, the activity of the sample is nearly equal to:

1.  ${10}^4$ $Bq$

2.  ${10}^5$ $Bq$

3.  ${10}^6$ $Bq$

4.  ${10}^3$ $Bq$

For the given reaction, the particle \(\mathrm{X}\) is:
\({ }_6^{11} \mathrm{C}\rightarrow { }_5^{11}\mathrm{B}+\beta^{+}+\mathrm{X}\)
1. neutron
2. anti-neutrino
3. neutrino
4. proton

The relation between λ and T_1/2 is:
(T_1/2 = half-life, λ → decay constant)

1. $T_{1/2}=\frac{\ln 2}{\lambda }$

2. $T_{1/2}$ $\ln 2=\lambda$

3. $T_{1/2}=\frac{1}{\lambda }$

4. $(\lambda +T_{1/2})=\frac{\ln }{2}$

If the half-life of a radionuclide is 77 days, then its decay constant is:
1.  0.003/day
2.  0.006/day
3.  0.009/day
4.  0.012/day

Which of the following are suitable for the fusion process?

The half-life of a sample of a radioactive element containing 4 × 10¹⁶ active nuclei, is 10 days. The number of decayed nuclei after 30 days will be: 

1. $0.5\times {10}^{16}$

2. $2\times {10}^{16}$

3. $3.5\times {10}^{16}$

4. $1\times {10}^{16}$