Tag: physics

Questions Related to physics

As the mass number increase, binding energy per nucleon,

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. increases

  2. decreases

  3. remain same

  4. may increase or may decrease

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Correct Option: D

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:

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $29.6 \mathrm { MeV }$

  2. $2.4MeV$

  3. $8.4 \mathrm { MeV }$

  4. $17.3 \mathrm { MeV }$

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Correct Option: A

Mass defect of an atom refers to 

nuclear reactions nuclear structure nuclei atomic nuclei physics

  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

Show answer
Correct Option: B
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

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

nuclear reactions nuclear structure nuclei atomic nuclei physics

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

Show answer
Correct Option: A
Explanation:

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

For uranium nucleus. Find relation between mass and volume 

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $m\propto v$

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

  3. $m\propto v^2$

  4. $m\propto \dfrac{1}{v}$

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Correct Option: A

The phenomenon of pair production is :

nuclear reactions nuclear structure nuclei atomic nuclei physics

  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

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Correct Option: A
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.

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

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  1. 2

  2. 3

  3. 4

  4. 1

Show answer
Correct Option: A
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.

The rest energy of electron or positron is

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. 0.51 MeV

  2. 1 MeV

  3. 1.02 MeV

  4. 1.5 MeV

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Correct Option: A
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$

Positronium is converted into

nuclear reactions nuclear structure nuclei atomic nuclei physics

  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

Show answer
Correct Option: A
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.

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

nuclear reactions nuclear structure nuclei atomic nuclei physics

  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

Show answer
Correct Option: B
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.