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 binding energy per nucleon of deutron $(^2 _1 H)$ and helium nucleus $(^4 _2 He)$ is 1.1 MeV and 7 MeV respectively. If two deutron 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(He) - 2 * BE(deuteron) = (4 * 7) - 2 * (2 * 1.1) = 28 - 4.4 = 23.6 MeV.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Binding energy per nucleon is $8.5 \text { MeV for } A = 120$ and is $7.6 \mathrm { MeV } \text { for } \mathrm { A } = 240$ Suppose a nucleus with $A = 240$ breaks into two nuclei of nearly equal mass numbers then which of the following is correct

  1. 216 MeV energy is released.

  2. 21 MeV energy is to be given from outside

  3. 220 MeV energy is released.

  4. no energy is released.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Initial BE = 240 * 7.6 = 1824 MeV. Final BE = 2 * (120 * 8.5) = 2 * 1020 = 2040 MeV. Energy released = 2040 - 1824 = 216 MeV.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Consider the nuclear reaction: $\mathrm { X } ^ { 200 } \longrightarrow \mathrm { A } ^ { 110 } + \mathrm { B } ^ { 20 }$If the binding energy per nucleon for $\mathrm { X } , \mathrm { A }$ and $\mathrm { B }$ is $7.4 \mathrm { MeV } , 8.2 \mathrm { MeV }$ and 8.2$\mathrm { MeV }$ respectively, what is the energy relesed?

  1. $200$ $\mathrm { MeV }$
  2. $160$ $\mathrm { MeV }$
  3. $110$ $\mathrm { MeV }$
  4. $90$ $\mathrm { MeV }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

In the nucleus of helium if ${ F } _{ 1 }$ is the net force between two protons ${ F } _{ 2}$ is the net force between two neutrons and ${ F } _{ 3 }$ is the net force between a proton and a neutron. Then,

  1. ${ F } _{ 1 }={ F } _{ 2 }={ F } _{ 3 }$
  2. ${ F }> _{ 1 }{ F } _{ 2 }{ >F } _{ 3 }$
  3. ${ F }> _{ 2 }{ F } _{ 3 }{ >F } _{ 1 }$
  4. ${ F } _{3}={ F } _{ 1 }{ >F } _{ 2 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nuclear forces are the strong forces of attraction which hold together the nucleons (neutrons and protons) in the tiny nucleus of an atom, inspite of strong electrostatic forces of repulsion between protons. Nuclear forces act between a pair of neutrons, a pair of protons and also between a neutron, proton pair with the same strength. This shows that nuclear forces are independent of charge. 
The attractive nuclear force is the same for any pair of nucleons. Thus$ F _1 = F _3$ when there are no electrostatic forces, but $F _2 =$ attractive nuclear force - repulsive electrostatic force
Hence
$F _3 = F _1 > F _2$
Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The binding energy of $\alpha $-particle is ( if ${ m } _{ p }=1000785$ $u,{ m } _{ n }=1.00866$ u and ${ m } _{ \alpha  }=4.00274u$)

  1. $56.42 MeV$
  2. $2.821 MeV$
  3. $28.21 MeV$
  4. $32.4 MeV$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Mass defect: Δm = (2mp + 2mn) - mα = 2(1.00785) + 2(1.00866) - 4.00274 = 0.03028 u. BE = Δm × 931.5 MeV/u = 0.03028 × 931.5 ≈ 28.21 MeV. Note: Problem shows mp = 1000785 u which appears to be a typo for 1.00785 u.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The energy released when a positron is annihilated is

  1. $0.51 MeV$
  2. $0.58 MeV$
  3. $185 MeV$
  4. $200 MeV$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Positron, also called positive electron,  positively charged subatomic particle having the same mass and magnitude of charge as the electron.

mass of $e^+ = 9.11\times 10^{-31}Kg$

$E =mc^2=  9.11\times 10^{-31}\times (3\times 10^8)^2  J$

                 $= {0.51  \ MeV}$

The energy of annihilation of positron is ${0.51 \ MeV}$.
Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Assertion (A) : Due to annihilation of electron positron pair, at least 2 $\gamma $-ray photons are produced.
Reason (R) : This is in accordance with conservation of linear momentum.

  1. Both A & R are true and R is the correct explanation of A

  2. Both A & R are true and R is not correct explanation of A

  3. A is true but R is false

  4. A is false but R is true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$ e^{-} + e^{+} \Rightarrow  \gamma +\gamma $
This annihilation is in accordance to three laws:-
1] conservation of linear momentum
2] conservation of charge
3] conservation of angular momentum
Two $\gamma $ ray photons are released on annihilation of electron and positron.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Choose the correct statement :

  1. A nucleus is relatively more stable for which total binding energy is more.

  2. A nucleus is relatively more stable for which binding energy per nucleon is more.

  3. A nucleus is relatively more stable for which total binding energy is low.

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Binding energy is the amount of energy required to separate a particle from a system of particles or to disperse all the particles of the system. Binding energy is especially applicable to subatomic particles in atomic nuclei, to electrons bound to nuclei in atoms, and to atoms and ions bound together in crystals. Binding energy is more if the nucleus is relatively more stable.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The binding energy per nucleon of deuteron $ \left( \frac { 2 }{ 1 }  H \right)  $ and helium nucleus $ \left( \frac { 4 }{ 2 } He \right)  $ is.1.1 meV and 7 meV respectively. If two deuteron nuclei react to from s single helium nucleus, then the energy released is:

  1. 13.9 MeV

  2. 26.9 MeV

  3. 23.6 MeV

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

Total binding energy of two deuterons = 2 × 2.2 = 4.4 MeV. Total binding energy of helium = 4 × 7 = 28 MeV. Energy released = 28 - 4.4 = 23.6 MeV. Note: This is another duplicate with 'meV' typo (should be MeV).

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

The binding energy expressed in $MeV$ is given for the following nuclear reactions :
$ _2He^3+\ _0n^1\rightarrow\ _2He^4+20\ MeV$
$ _2He^4+\ _0n^1 \rightarrow\ _2He^5 -0.9\ MeV$
Which of the following conclusions are correct ?

  1. $ _2He^4$ is less stable than both $ _2He^3$ and $ _2He^5$
  2. $ _2He^4$ is less stable than $ _2He^3$ but more stable than $$ _2He^5$
  3. $ _2He^4$ is less stable than $ _2He^5$ but more stable than $$ _2He^3$
  4. $ _2 He^4$ is more stable than both $ _2He^3$ and $ _2He^5$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A positive energy release (Q > 0) indicates a stable product, while a negative energy release (Q < 0) indicates an unstable product. Since the first reaction releases 20 MeV, He-4 is more stable than He-3. Since the second reaction requires 0.9 MeV, He-5 is less stable than He-4.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

In nuclear reaction
$ _{2}He^{4}+\ _{Z}X^{A}\rightarrow Z+\  _{2}\gamma^{A+3}+\ _{Z}M^{A}$
where $M$ denotes

  1. electron

  2. positron

  3. proton

  4. neutron
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In the reaction, we need to identify what M represents. Based on nuclear reaction notation and the fact that it appears after the product nucleus, M is a neutron that is emitted in the reaction. The reaction shows helium-4 bombarding target X, producing an excited nucleus that emits gamma rays and a neutron.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

A parent nucleus $^{m} _{1}p$ decays into a daughter nucleus $D$ through $\alpha$ emission in the following way $^{m} _{1}p\rightarrow D+\alpha$ The subscript and superscript on the daughter nucleus $D$ will be written as

  1. $^{m} _{n}D$
  2. $^{m+4} _{n}D$
  3. $^{m-4} _{n}D$
  4. $^{m-4} _{n-2}D$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Alpha decay involves the emission of a helium nucleus, which has a mass number of 4 and an atomic number of 2. Therefore, the daughter nucleus must have a mass number reduced by 4 and an atomic number reduced by 2.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

In which of the following nuclear reactions, the product is incorrectly matched ?

  1. $ _{96}Cm^{242}(\alpha, 2n) _{97}Bk^{243}$
  2. $ _5B^{10}(\alpha, n) _7N^{13}$
  3. $ _7N^{14}(n, p) _6C^{14}$
  4. $ _{14}Si^{28}(d, n) _{15}P^{29}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In option A, the mass number change is 243-242 = 1, but the reaction is (alpha, 2n). An alpha particle adds 4 to the mass and 2 to the atomic number, while 2 neutrons remove 2 from the mass. The net change should be +2 mass and +2 atomic number, making the product Cm-242 + He-4 - 2n = Bk-244, not Bk-243.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

$A5\times 10^{-4}\overset {o}{A}$ photon produces an electron-positron pair in the vicinity of a heavy nucleus. Rest energy of electron is 0.5 11 MeV. If they have the same kinetic energies, the energy of each particle is nearly

  1. 1.2 MeV

  2. 12 MeV

  3. 120 MeV

  4. 1200 MeV
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Photon wavelength: λ = 5 × 10⁻⁴ Å = 5 × 10⁻¹⁴ m. Energy: E = hc/λ = (1240 eV·nm)/(5 × 10⁻⁵ nm) ≈ 24.8 MeV. Total rest energy of e⁻e⁺ pair: 2 × 0.511 = 1.022 MeV. Available kinetic energy: 24.8 - 1.022 ≈ 23.78 MeV. Each particle gets half: ≈ 11.89 MeV, approximately 12 MeV. Note: '0.5 11 MeV' appears to be typo for 0.511 MeV.