Tag: nuclear physics

Questions Related to nuclear physics

Which decay increases the atomic number?

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. Alpha decay

  2. ${\beta}^{-}$ decay

  3. ${\beta}^{+}$ decay

  4. Electron capture

  5. Gamma decay

Show answer
Correct Option: B
Explanation:

$\beta^-$ decay : $^A _ZX \rightarrow ^A _{Z+1}Y $ $+ $  $ _{-1}^0e $

Thus, the atomic number is increased in $\beta^-$ decay.

What would be an atom that has lost an electron?

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. Positron

  2. Negatron

  3. Baryon

  4. Hadron

  5. Ion

Show answer
Correct Option: E
Explanation:

We know that an atom is electrically neutral because it has equal number of electrons(negative charge) and protons(positive charge) , now when it has lost an electron , negative charge decreases in the atom hence the net charge is now positive, the atom would be an ion.

For which of the following events will the resulting products have more mass than the mass of the stuff from which the products came?

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. Alpha decay

  2. Beta decay

  3. An exothermic nuclear reaction

  4. An endothermic nuclear reaction

  5. Nuclear fission of uranium $-235$

Show answer
Correct Option: D
Explanation:

In an endothermic nuclear reaction, heat energy is given to the reaction to proceed and thus according to Einstein's mass-energy equivalence law, heat energy given gets converted into additional mass which results in the formation of products with more mass than the reactants.

The equation $ _{88}Ra^{226}\rightarrow _{86}Rn^{222}+ _{2}He^{4}$ emits which particle?

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. $\beta$-decay

  2. $\alpha$-decay

  3. $\gamma$-decay

  4. None of the above

Show answer
Correct Option: B
Explanation:

$\alpha $ - decay 

When an unstable atomic nucleus emits two protons and two neutrons the radioactive process is known as alpha decay. 

During $\beta^-$ emission:

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. a neutron in the nucleus decays emitting an electron

  2. an atomic electron is ejected

  3. an electron already present within the nucleus is ejected

  4. a part of the binding energy of the nucleus is converted into an electron

  5. a proton in the nucleus decays emitting an electron

Show answer
Correct Option: A
Explanation:

$\beta^-$ emission is due to decay of neutron in the nucleus $n\rightarrow p+e^-$.

Nuclei of a radioactive element $A$ are being produced at a constant rate $\alpha$. The element has a decay constant $\lambda$. At $t =0$, there are $N _{0}$ nuclei of the element.
If $\alpha = 2N _{0}\lambda$, calculate the number of nuclei of $A$ after one half life of $A$, and also the limiting value of $N$ as $t\rightarrow \infty$.

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. $\dfrac {4N _{0}}{2}, 2N _{0}$.

  2. $\dfrac {3N _{0}}{2}, 2N _{0}$.

  3. $\dfrac {5N _{0}}{2}, 2N _{0}$.

  4. $\dfrac {6N _{0}}{2}, 2N _{0}$.

Show answer
Correct Option: B

$90$% of a radioactive sample is left undecayed after time $t$ has elapsed. What percentage of the intial sample will decay in a total time $2t$:

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. $20$%

  2. $19$%

  3. $40$%

  4. $38$%

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Correct Option: B

$ _{84}P _{0}^{210}$ originally at rest emits $\alpha $- particles of KE 'K' Find  the KE of recoiling nucleus:

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. $\dfrac{4}{214}K$

  2. $\dfrac{4}{206}K$

  3. $\dfrac{K}{206}$

  4. $\dfrac{K}{214}K$

Show answer
Correct Option: B
Explanation:

$84P _o^{210}\xrightarrow 82Pb^{206}+\alpha \Rightarrow $ mass of remaining nucleus $(Pb)=206$

Initial momentum =$0$ (initial Po was at rest)
Momentum of $\alpha$- particle carrying $KE=K$
$P _1\sqrt{2m _{\alpha}k}$     $m _{alpha}=4n$,mass of $\alpha$
$P _1=\sqrt{8k}$
from conservation of momentum
$P _1+P _2=0$
$\Rightarrow P _1^2=P _2^2$
$2\ mrk'=2k$
$K'=\dfrac{4k}{mr}=\dfrac{4k}{206}$

When a radioactive nucleus emits a $\beta $- particular, the proton- neutron ratio

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. decreases

  2. increases

  3. remains same

  4. first decreases and increases

Show answer
Correct Option: B
Explanation:

When the neutron to proton ratio in the nucleus is too great a beta particle is emitted. In basic beta decay a neutron is transformed into a proton and an electron. The electron is then emitted as a beta particle which increases the atomic number by one and the molar mass is unchanged.

Hence, the proton- neutron ratio increase.

A free neutron is unstable against $\beta$ decay with a half life of about $600$ seconds:

physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

  1. The expression of this decay process in $n\rightarrow p+e^{-}+\vec{v}$

  2. If three are $600$ free neutrons initially, the time by which $450$ of them have decayed is $2400$ sec.

  3. The dacay rate of the sample is $0.593$ Bq.

  4. The dacay rate of the sample is $593$ Bq.

Show answer
Correct Option: C