Tag: physics

Questions Related to physics

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

nuclear reactions nuclear structure nuclei atomic nuclei physics

  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}$

Show answer
Correct Option: A

A proton and an alpha particle having same momentum enter a magnetic field at right angles to it. If $r _1$ and $r _2$ be their radii respectively then value of $r _1 /r _2$ is : 

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $1$

  2. $2$

  3. $1/2$

  4. $1/4$

Show answer
Correct Option: B

$A5\times 10^{-4}\overset {o}{A}$ 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

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. 1.2 MeV

  2. 12 MeV

  3. 120 MeV

  4. 1200 MeV

Show answer
Correct Option: B

If mass-energy equivalence is taken into account, when water is cooled to form ice, the mass of water should

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. increase

  2. remain unchanged

  3. decrease

  4. first increase then decrease

Show answer
Correct Option: A
Explanation:

Because thermal energy decreases, therefore mass should increase.

If 1mg of ${ U }^{ 235 }$ is completely annihilated, the energy liberated is

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $\quad 9\times { 10 }^{ 10 } J$

  2. $\quad 9\times { 10 }^{ 19} J$

  3. $\quad 9\times { 10 }^{ 18} J$

  4. $\quad 9\times { 10 }^{ 17} J$

Show answer
Correct Option: A
Explanation:

$E={ mc }^{ 2 }={ 10 }^{ -6 }\times \left( 3\times { 10 }^{ 8 } \right) ^{ 2 }={ 10 }^{ -6 }\times 9\times { 10 }^{ 16 }=9\times { 10 }^{ 10 }J$

One milligram of matter convert into energy will give

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $90 joule$

  2. $9\times { 10 }^{ 3} joule$

  3. $9\times { 10 }^{ 5} joule$

  4. $9\times { 10 }^{ 10} joule$

Show answer
Correct Option: D
Explanation:

$E={ mc }^{ 2 }={ 10 }^{ -3 }\times{ 10 }^{ -3 } \left( 3\times { 10 }^{ 8 } \right) ^{ 2 }=9\times { 10 }^{ 10 }J$

The mass and energy equivalent to $1 amu$ are respectively

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $1.67\times { 10 }^{ -27 }gm$, $9.30 MeV$

  2. $1.67\times { 10 }^{ -27 }kg$, $930 MeV$

  3. $1.67\times { 10 }^{ -27 }kg$,$ 1 MeV$

  4. $1.67\times { 10 }^{ -34 }kg$, $1 MeV$

Show answer
Correct Option: B
Explanation:

1 amu
It is defined as one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state.


Mass of 1 mole C atoms $= 12 gms$
$1\ amu = $$ \cfrac{12}{12 \times 6.023 \times 10^{23}} = 1.66 \times 10^{-27} kg$

Energy equivalent, $E = mc^2 =1.66 \times 10^{-27} kg \times (3 \times 10^8)^2$$ = 930\ MeV$

If an electron and positron annihilate, then the energy released is

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $3.2\times { 10 }^{ -13 } J$

  2. $1.6\times { 10 }^{ -13 } J$

  3. $4.8\times { 10 }^{ -13 } J$

  4. $6.4\times { 10 }^{ -13 } J$

Show answer
Correct Option: B
Explanation:

Energy of electron $={ m } _{ e }{ c }^{ 2 }$
Energy of positron $={ m } _{ p }{ c }^{ 2 }$
${ m } _{ e }$ = ${ m } _{ p }$, $ c=$ speed of light.

Thus according to conservation of energy released $=2{ m } _{ e }{ c }^{ 2 }$$=2\times 9.1\times { 10 }^{ -31 }\left( 3\times { 10 }^{ 8 } \right) ^{ 2 }=1.6\times { 10 }^{ -13 } Joules.$

The rest energy of an electron is

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $510 KeV$

  2. $931 KeV$

  3. $510 MeV$

  4. $931 MeV$

Show answer
Correct Option: A
Explanation:

Rest energy of an electron $=m _{ e }{ c }^{ 2 }$
Here $m _{ e }=9.1\times { 10 }^{ -31 }kg$ and $C$ = velocity of light

$\therefore$ Rest energy $=9.1\times { 10 }^{ -31 }\times\left( 3\times { 10 }^{ 8 } \right) ^{ 2 }joule$

                         $=\displaystyle \frac { 9.1\times { 10 }^{ -31 }\times \left( 3\times { 10 }^{ 8 } \right) ^{ 2 } }{ 1.6\times { 10 }^{ -19 } } eV\simeq 510KeV$

1mg of matter convert into energy will give

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $90$ joule

  2. $9\times { 10 }^{ 3 }$ joule

  3. $9\times { 10 }^{ 5 }$ joule

  4. $9\times { 10 }^{ 10 }$ joule

Show answer
Correct Option: D
Explanation:

$E=m{ c }^{ 2 }=10^{ -3 }\times { 10 }^{ -3 }\times { \left( 3\times { 10 }^{ 8 } \right)  }^{ 2 }= 9\times { 10 }^{ 10 }J$