Tag: physics

Questions Related to physics

A radio isotope X has a half life of $10s$. Find the number of active nuclei in the sample (if initally there are $1000$ isotopes which are falling from rest from a height of $3000m$) when it is at a height of $1000m$ from the reference plane: 

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

  1. $50$

  2. $250$

  3. $29$

  4. $100$

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Correct Option: B
Explanation:

Time taken in falling a height $h=3000-1000=2000m$ 

is given as $t=\sqrt[2]{\dfrac{2h}{g}}$
putting $g=10,h=2000$ we get $t=20second$
number of half life in this time period is $n=20/10=2$
So number of active nuclei$ = initial/2^n=initial/2^2=inital/4=1000/4=250$
Option B is correct.

When a $\beta^-$ particle is emitted from a nucleus, the neutron-proton ratio:

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

  1. is decreased

  2. is increased

  3. remains the same

  4. first (A) then (B)

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Correct Option: B
Explanation:

$ _{A}^{Z}\textrm{X}$ $\rightarrow  _{A-1}^{Z}\textrm{Y} $  $+  \beta^{-1}$


So,  the neutron-proton ratio before emission $ = \dfrac{Z-A}{A}$

And, the neutron-proton ratio after emission $ = \dfrac{Z-A+1}{A-1}$
Since, $ \dfrac{Z-A+1}{A-1}$  $ >\dfrac{Z-A}{A}$
Therefore, B is correct option.

A certain mass of an ideal diatomic gas contained in a closed vessel is heated. It is observed that half the amount of gets dissociated, but the temperature remains constant. The ratio of the heat supplied to the gas to the initial internal energy of the gas will be

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

  1. $1:2$

  2. $1:4$

  3. $1:5$

  4. $1:10$

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Correct Option: A

A positron is emitted by radioactive nucleus of proton number $90$. The product nucleus will have proton number :

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

  1. $91$

  2. $90$

  3. $89$

  4. $88$

Show answer
Correct Option: C
Explanation:

The given nuclear reaction is-

$ _{90}X \rightarrow   _{+1}e $  $+ $ $ _zY$ 
Using law of conservation of atomic (or proton) number:
$90 = 1 + Z$
$\implies$ $Z = 89$
Thus the product nucleus will have proton number $89$.

When $ _{15}P^{30}$ decays to become  $ _{14}Si^{30}$, which particle is released ?

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

  1. electron

  2. $\alpha$-particle

  3. neutron

  4. positron

Show answer
Correct Option: D
Explanation:

The nuclear reaction :   $ _{15}P^{30}\rightarrow$   ${14}Si^{30} + $  $ _{+1}e^0$

Thus a positron is emitted during the decay of  $ _{15}P^{30}$ into   $ _{14}Si^{30}$.

A nucleus $ _{  }^{ 220 }{ X }$ at rest decays emitting an $\alpha$- particle. If energy of daughter nucleus is $0.2MeV$, $Q$ value of the reaction is

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

  1. $10.8MeV$

  2. $10.9MeV$

  3. $11MeV$

  4. $11.1MeV$

Show answer
Correct Option: A

The antiparticle of electron is

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

  1. positron

  2. $\alpha $-particle

  3. proton

  4. $\beta $-particle

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Correct Option: A
Explanation:

Antiparticle of electron $ _{ -1 }{ e }^{ 0 }$ is positron $ _{ +1 }{ e }^{ 0 }$

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.