Alpha Decay

Q. Tritium has a half life of 12.5 years undergoing beta decay. What fraction of sample of pure tritium will decay in 50 years?

1. $\frac{3}{4}$
2. $\frac{15}{16}$
3. $\frac{63}{64}$
4. $\frac{7}{8}$

Q. In a radioactive decay chain, ​${}_{90}^{232}Th$ nucleus decays to ${}_{82}^{212}Pb$ nucleus. Let $N_{\alpha }$ ​ and $N_{\beta }$ ​ be the number of α and ${\beta }^{-}$ particles respectively, emitted in this decay process. Which of the following statements is (are) true?

1. $N_{\alpha }=5$
2. $N_{\alpha }=6$
3. $N_{\beta }=2$
4. $N_{\beta }=4$

Q. The activity of a sample of a radioactive material is $A_1$ at time $t_1$ and $A_2$ at time $t_2(t_2>t_1)$. If its mean is life T, then

1. $A_1{t}_1=A_2{t}_2$
2. $A_1-A_2=t_2-t_1$
3. $A_2=A_1{e}^{\frac{(t_1-t_2)}{T}}$
4. $A_2=A_1{e}^{\frac{(t_1-t_2)}{T}}$

Q. What is the composition of an $\alpha$
particle?

1. 2 protons and 2 neutrons only
2. 2 electrons, 2 protons and 2 neutrons
3. 2 electrons and 4 protons only
4. 2 protons only

Q. The element Lawrencium ${(}_{103}^{256}Lr)$ is named after Ernest Lawrence, whose invention - the cyclotron - helped discover many radioactive nuclei. Consider now, the alpha decay of ${}_{103}^{256}Lr$:
${}_{103}^{256}Lr{\to }_b^{a}Md+\alpha ,$
Where $\alpha$ represents the alpha particle given out. What are the values of a and b?

1. a=252; b=105
2. a=252; b=101
3. a=260; b=101
4. a=260; b=105

Q. Which of these is at a higher energy level in alpha decay?

1. Parent Nucleus
2. Daughter Nucleus and Alpha particle
3. Both are equal
4. Depends on the particular case

Q. What will be the daughter nuclei after 4 alpha decays of ${}_{91}^{231}Pa$

1. ${}_{89}^{227}X$
2. ${}_{83}^{215}X$
3. ${}_{75}^{215}X$
4. $\text{None of these}$

Q. The Kinetic Energy after an alpha decay is mainly carried by the alpha particle.

1. True
2. False

Q.

Don't hate me for asking this question, as it will need you to work your calculator! So, in the radioactive decay -
${}^{238}Pu{\to }^{234}U+\alpha ,$
What will be the kinetic energy of the outgoing α-particle?
Things you will need:

• Atomic masses: $m{(}^{238}Pu)=238.04955u;m{(}^{234}U)=234.04095u;m{(}^{4}He)=4.002603u.$
• Constant: $c^2=931\frac{MeV}{u}.$

1. 5.58 MeV

2. 4.72 MeV

3. 5.03 MeV

4. 3.34 MeV