Tag: nuclear reactions

Quizzes (0) Questions (103)

Questions Related to nuclear reactions

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The phenomenon of pair production is :

  1. The production of an electron and a positron from $\gamma$ radiation

  2. Ejection of an electron from a metal surface when exposed to ultraviolet light

  3. Ejection of an electron from a nucleus

  4. Ionization of a neutral atom
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pair production :
Gamma rays of sufficient energy when passing near a nucleus disappear and materialize into pair of an electron and a positron.
To have pair production, minimum energy of $\gamma$ - ray radiation is 1.02MeV.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

In pair annihilation the least number of  $\gamma $- ray photons produced is :

  1. 2

  2. 3

  3. 4

  4. 1
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a pair annihilation, atleast two gamma rays must be produced. For example, when an electron encounters a positron, they annihilate to produce two gamma rays each having $0.511$ MeV energy.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The rest energy of electron or positron is

  1. 0.51 MeV

  2. 1 MeV

  3. 1.02 MeV

  4. 1.5 MeV
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Mass of electron $ = 9.1 \times 10^{-31}  kg$

Rest mass energy $ = mc^{2}$


                               $ =\left (\dfrac{9.1\times 10^{-31}}{1.6\times10^{-27}} \times931.978\right )c^{2}$

                               $ = 0.52\  MeV$

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Positronium is converted into

  1. 2 Photons each of energy 0.51MeV

  2. 1 Photon of energy 1.02 MeV

  3. 2 Photons each of energy 1.02MeV

  4. 1 Photon of energy 0.51MeV
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Rest mass energy of a positron (as well as electron) is $0.51$ MeV.

Total rest mass energy of positron and electron is $2(0.51) = 1.02$ MeV
Thus a positron and an electron annihilate to produce two photons each of energy $0.51$ MeV. This phenomenon is known as positron-electron annihilation process.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

In pair annihilation, two  $\gamma $ -ray photons are produced due to

  1. Law of conservation of energy

  2. Law of conservation of mass

  3. Law of conservation of momentum

  4. Law of conservation of angular momentum
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a particle encounters its antiparticle, they annihilate with the transformation of their mass energies into two gamma rays obeying law of conservation of mass.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Which one of the following cannot be used as a moderator in a nuclear reactor?

  1. Water

  2. Heavy water

  3. Molten sodium

  4. Graphite
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Commonly used moderators in nuclear reactors include water, heavy water (D2O), and graphite, which slow down fast neutrons effectively. Molten sodium is used as a coolant to transfer heat from the reactor core, not as a moderator.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Which row describes the nature of $\alpha$- particles and of $\gamma$- rays

  1. $\alpha$- particles : helium nuclei ; $\gamma$ rays - electromagnetic radiation
  2. $\alpha$- particles : helium nuclei ; $\gamma$ rays - electrons
  3. $\alpha$- particles : protons; $\gamma$ rays - electromagnetic radiation
  4. $\alpha$- particles : protons; $\gamma$ rays - electrons
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Characteristics of $\alpha$ particle
  mass= $4$ unit
  charge = $+2$ unit
The mass of Helium nuclei is $4$ unit and charge is $+2$ unit. So, it is equivalent to $\alpha $ particle .

$\gamma $- rays  is a penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei.
Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

A scientist carries out an experiment using a sealed source which emits $\beta$ -particles. The range of the $\beta$- particles in the air is about $30cm$.
Which precaution is the most effective to protect the scientist from the radiation?

  1. handling the source with long tongs

  2. keeping the temperature of the source low

  3. opening all windows in the laboratory

  4. washing his hands before leaving the laboratory
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Handling the source with long tongs will prevent him from the exposure of $\beta$- particles. Since the range of $\beta$-particle is only $30cm$ so, long tongs can easily be a safer and effective precaution.