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Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

As the mass number increase, binding energy per nucleon,

  1. increases

  2. decreases

  3. remain same

  4. may increase or may decrease
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The binding energy per nucleon curve rises sharply for light nuclei, peaks around iron (mass number 56), and then gradually decreases for heavier nuclei.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Per nucleon energy of $ _ { 3 } L ^ { 7 }$ and $2 ^ { \mathrm { H } e ^ { 4 } }$  nucleus is 5. 60  MeV and 7.06 MeV then in$ _ { 3 } \mathrm { L } ^ { 7 } + _ { 1 } \mathrm { P } ^ { 1 } \rightarrow 2 _ { 2 } \mathrm { He } ^ { 4 }$ energy released is:

  1. $29.6 \mathrm { MeV }$

  2. $2.4MeV$

  3. $8.4 \mathrm { MeV }$

  4. $17.3 \mathrm { MeV }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Mass defect of an atom refers to 

  1. inaccurate measurement of mass of neutrons

  2. mass annihilated to produce energy to bind the nucleons

  3. packing fraction

  4. difference in the number of neutrons and protons in the nucleus
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$ Mc^{2} + (B.E) = (N _{mN} + Z _{mP})c^{2}$
where,
         $M _{c} =  $  total mass of nucleus.
         $N _{mN} =  $  total mass of neutrons
         $N _{mP}  =  $  total mass of protons

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

In a fission process, nucleus A divides into two nuclei B and C, their binding energies being $\mathbf { E } _ { \mathbf { a } ^ { * } }$   $E _ { b }$  and $E _ { c }$ respectively. Ihen

  1. $\mathbf { E } _ { \mathrm { b } } + \mathrm { E } _ { \mathrm { c } } = \mathrm { E } _ { \mathrm { a } }$

  2. $\mathrm { E } _ { \mathrm { b } } + \mathrm { E } _ { \mathrm { c } } > \mathrm { E } _ { \mathrm { a } }$

  3. $\mathrm { E } _ { \mathrm { b } } + \mathrm { E } _ { \mathrm { e } } < \mathrm { E } _ { \mathrm { a } }$

  4. $\mathrm { E } _ { \mathrm { b } } \mathrm { E } _ { \mathrm { c } } = \mathrm { E } _ { \mathrm { a } }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\begin{array}{l} { E _{ b } }+{ E _{ c } }>{ E _{ a } } \ \, \because some\, \, energy\, \, is\, \, goen\, \, in\, \, breaking\, \, nuclie\, \, of\, \, A \ Hence, \ option\, \, A\, \, is\, \, correct\, \, answer. \end{array}$

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

For uranium nucleus. Find relation between mass and volume 

  1. $m\propto v$

  2. $m\propto \sqrt{v}$

  3. $m\propto v^2$

  4. $m\propto \dfrac{1}{v}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nuclear density is constant, so mass m = density * volume. Therefore, m is directly proportional to volume (m proportional to v).

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.