Physics

Nuclear and Atomic Physics

571 Questions

Nuclear and atomic physics explores the components and properties of the nucleus, including isotopes, radioactive decay, and fundamental forces. These concepts are essential for various competitive exams requiring a strong foundation in physics. The provided questions cover structural properties, mass, energy equivalence, and particle interactions.

Nucleus propertiesIsotopes and mass numberAlpha particle scatteringNuclear forcesMass energy equivalenceBeta particle emission

Nuclear and Atomic Physics Questions

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 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

How much energy is released when a $ _{8}{O}^{16}$ nucleus is completely converted into energy?

The binding energy per nucleon of $ _{8}{O}^{16}$ is $7.97  MeV$ and ${m} _{p} = 1.0078  u$ and ${m} _{n} = 1.0087  u$

  1. $14899.438 MeV$
  2. $148.99 MeV$
  3. $4489.73 MeV$
  4. $448.973 MeV$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Binding Energy $=E=\triangle mc^2$
$\triangle m=$ mass of nucleus $-$ (mass of proton + neutron)
Multiplying both sides by $c^2$
$\triangle mc^2=$ (mass of nucleus)$c^2 -$ (mass of proton + neutron)$c^2$
$=7.97\times 16-8(1.0078+1.0087)931 \\ E=127.52-15018.892 \\ E=-14899.438MeV$
Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Which of the following assertions are correct?

  1. A neutron can decay to a proton only inside a nucleus

  2. A proton can change to a neutron only inside a nucleus

  3. An isolated neutron can change into proton

  4. An isolated proton can change into a neutron
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A free proton is stable. A proton inside a nucleus can change into a neutron via beta-plus decay or electron capture to reach a more stable state.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Inside nucleus, protons are held together though they have the dame charge. Why?

  1. The strong attractive nuclear force far exceeds the electrostatic force between the protons

  2. Neutrons prevent them from repelling from each other

  3. The electrostatic attractive force between an electron and a proton is more than the electrostatic repulsive force between the protons

  4. Gluons are responsible for holding them together
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Protons within a nucleus experience strong electrostatic repulsion due to their positive charges. The strong nuclear force, which is an attractive force acting between nucleons at very short ranges, is significantly stronger than this electrostatic repulsion, thereby holding the nucleus together.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Magnitude of mass defect is a measure of ......................... of a nucleus.

  1. Unstability

  2. Stability

  3. Charge

  4. Position
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mass defect represents the difference between the mass of a nucleus and the sum of the masses of its individual nucleons. A larger mass defect corresponds to a higher binding energy per nucleon, which indicates greater nuclear stability.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

In a hypothetical star,two carbon nuclei fuse to form magnesium.The reaction is:(take :$1amu=931MeV/c^2)$
$^{12}C+^{12}C\rightarrow ^{24}Mg$
The energy released per carbon nuclei is: (Mass of $^{24}Mg=23.985amu)$

  1. $13.965 MeV$
  2. $11.12 MeV$
  3. $6.982 MeV$
  4. $10.12 MeV$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$^{12}C+^{12}C\rightarrow ^{24}Mg$
mass of $^{12}C=12.0642 amu$
Total input mass $m _1=2\times 12.0642$
$=24.1284$ amu
Mass of $^{24}Mg$=output mass
$=m _0=23.955$
mass loss $=m _1-m _o$
$Am=24.1284-23.985$
$=0.1434 amu$
Energy released $=0.1434\times 931 Mev$
$=13.965 Mev$

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

In the nuclear reaction ; $ _{92}U^{238}\rightarrow _{z}Th^{A}+ _{2}He^{4}$ the values of A and Z are: 

  1. A=230,Z=8

  2. A=234,Z=90

  3. A=228, Z=94

  4. A=232, Z=
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In alpha decay, the mass number decreases by 4 and the atomic number decreases by 2. For U-238, A becomes 238 - 4 = 234 and Z becomes 92 - 2 = 90.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Out side a nucleus 

  1. Neutron is stable

  2. Proton and neuron both are stable

  3. Neutrons is unstable

  4. Neither neutrons nor proton is stable
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Free neutrons outside a nucleus are unstable and decay with a half-life of about 10.2 minutes. Protons, however, are stable particles. The statement 'Neutrons is unstable' (despite the grammatical error) correctly identifies that free neutrons undergo beta decay.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The energy of the reaction ${ Li }^{ 7 }+p\longrightarrow 2{ He }^{ 4 }$ is (the binding energy per nucleon in ${ Li }^{ 7 }$ and ${ He }^{ 4 }$ nuclei are 5.60 and 7.06 MeV respectively.)

  1. 17.3 MeV`

  2. 1.73 MeV

  3. 1.46 MeV

  4. Depends on binding energy of proton
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The energy released will depend on the energy equivalent of proton, taking its mass to be $1amu$ or
 corresponding energy as $931.5Mev$
we get energy released as $Q=E _{reactant} -E _{product}=7\times 5.6 +931.5 -2\times4\times  7.06=914.22Mev$

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The binding energy per nucleon of deuteron $(^2 _1 H)$ and helium nucleus $(^4 _2 He)$ is 1.1 MeV and 7 MeV respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is

  1. 23.6 MeV

  2. 26.9 MeV

  3. 13.9 MeV

  4. 19.2 MeV
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Energy released = BE(products) - BE(reactants). BE(He) = 4 * 7 = 28 MeV. BE(2 deuterons) = 2 * (2 * 1.1) = 4.4 MeV. Energy released = 28 - 4.4 = 23.6 MeV.