Tag: physics

Questions Related to physics

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$^{2}$

Show answer
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

Show answer
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. $448.973 MeV$

Show answer
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

Show answer
Correct Option: B
Explanation:

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

Using $E = m{c}^{2}$, find out the energy released, when $2  u$ of mass is destroyed completely.
Take $1  u = 1.66 \times {10}^{-27}  kg$.

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $4.65 MeV$

  2. $3627 MeV$

  3. $91.5 MeV$

  4. $1865 MeV$

Show answer
Correct Option: D
Explanation:
When $2u$ of mass is destroyed completely then
$\triangle m=2u\\ E=\triangle m{ c }^{ 2 }\\ E=2\times 931MeV\\ \therefore 1u=931Mev/{ c }^{ 2 }\\ So,E=1863MeV\approx 1865MeV$
So, (D) is correct option.
What  describe the Einsteins equation for the relativity of mass and energy ?
nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. a small amount of mass contains a lot of energy.

  2. a small amount of energy can be converted into a large amount of mass.

  3. a small amount of mass contains a small amount of energy.

  4. mass can be converted into energy, but energy cannot be converted mass.

  5. energy can be converted into mass, but mass cannot be converted into energy.

Show answer
Correct Option: A
Explanation:

Sir Einstein's mass-energy equation states that mass and energy can be converted into each other by the following relation.

                 $E=mc^{2}$,    ($c=$speed of light)
This implies that a small amount of mass contains a lot of energy, which can be proved with an example.
Let we have a mass of $1g=10^{-3}kg$ , therefore energy produced by it will be:
                      $E=10^{-3}\times \left(3\times10^{8}\right)^{2}=9\times10^{13}J$ 
which is a vast amount energy produced by only one gram (small mass) of mass.
Whereas a small amount of energy doesn't give a large amount of mass because for that we have to divide the energy by $c^{2}$, which gives a small mass.