Tag: nuclei

Questions Related to nuclei

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

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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

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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.

To produce pair production, the minimum energy of $\gamma $-ray should be 

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. 0.15 MeV

  2. 1 MeV

  3. 1.02 MeV

  4. 1.5 MeV

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Correct Option: C
Explanation:

Minimum energy to produce pair production should be 1.02 MeV.

The energy equivalent of 1mg of mass in joule is

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. 3 x 10$^{2}$

  2. 3 x 10$^{10}$

  3. 9 x 10$^{10}$

  4. 9 x 10$^{2}$

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Correct Option: C
Explanation:

As, $m=10^{-6}\ kg$

using, $E=mc^2$
$E= 10^{-6} \ \times (3\times 10^8)^2 $
$E=9\times10^{10}J$

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

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. Water

  2. Heavy water

  3. Molten sodium

  4. Graphite

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Correct Option: A

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

nuclear reactions nuclear structure nuclei atomic nuclei physics

  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

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Correct Option: A
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.

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?

nuclear reactions nuclear structure nuclei atomic nuclei physics

  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

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Correct Option: A
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.

One electron volt is equal to .......................

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $\displaystyle 1.6\times 10^{-19}$ Joule

  2. $\displaystyle 16\times 10^{-19}$ Joule

  3. $\displaystyle 1.6\times 10^{-10}$ Joule

  4. $\displaystyle 1.6\times 10^{-9}$ Joule

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Correct Option: A

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 ${m} _{n} = 1.0087  u$

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $14899.438 MeV$

  2. $148.99 MeV$

  3. $4489.73 MeV$

  4. $448.973 MeV$

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Correct Option: A
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)$c^2$
$=7.97\times 16-8(1.0078+1.0087)931 \\ E=127.52-15018.892 \\ E=-14899.438MeV$

What is the energy required to increase the mass of a system by one atomic mass unit?

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. 661.5 MeV

  2. 931.5 MeV

  3. 1336.5 MeV

  4. 785.2 MeV

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Correct Option: B
Explanation:

$\Delta m = 1  u$
$E = 1 \times 931.5  MeV = 931.5  MeV$