Tag: nuclear structure

Questions Related to nuclear structure

$\gamma $ -ray photon of following energy undergoes pair production : 

a) $0.85Mev $      b) $1.00Mev $
c)  $1.02Mev $     d) $1.82Mev$

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. a,b

  2. c,d

  3. b,c,d

  4. only d

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Correct Option: B
Explanation:

The pair production becomes possible with gamma energies exceeding $1.02\ MeV$, and becomes important as an absorption mechanism at energies over $5\ MeV$.

Assertion (A) : Due to annihilation of electron positron pair, at least 2 $\gamma $-ray photons are produced.
Reason (R) : This is in accordance with conservation of linear momentum.

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. Both A & R are true and R is the correct explanation of A

  2. Both A & R are true and R is not correct explanation of A

  3. A is true but R is false

  4. A is false but R is true

Show answer
Correct Option: A
Explanation:

$ e^{-} + e^{+} \Rightarrow  \gamma +\gamma $
This annihilation is in accordance to three laws:-
1] conservation of linear momentum
2] conservation of charge
3] conservation of angular momentum
Two $\gamma $ ray photons are released on annihilation of electron and positron.

Choose the correct statement :

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. A nucleus is relatively more stable for which total binding energy is more.

  2. A nucleus is relatively more stable for which binding energy per nucleon is more.

  3. A nucleus is relatively more stable for which total binding energy is low.

  4. None of these

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Correct Option: A
Explanation:

Binding energy is the amount of energy required to separate a particle from a system of particles or to disperse all the particles of the system. Binding energy is especially applicable to subatomic particles in atomic nuclei, to electrons bound to nuclei in atoms, and to atoms and ions bound together in crystals. Binding energy is more if the nucleus is relatively more stable.

In the nuclear reaction : $X(n, \alpha) _3 Li ^7$ the term X will be 3

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $ _5{B}^{10}$

  2. $ _5{B}^{9}$

  3. $ _5{B}^{11}$

  4. $ _2{He}^{4}$

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Correct Option: B

The energy equivalent to $1kg$ of matter in (in Joule)

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $10^{17}$

  2. $19^{20}$

  3. $10^{11}$

  4. $10^{14}$

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Correct Option: A
Explanation:

Einstein mass -energy relation : $E=mc^2=1\times (3\times 10^8)^2=9\times 10^{16} \sim 10^{17}$ J

$1$ $a.m.u$ is equivalent to 

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $931$ $MeV$

  2. $139$ $MeV$

  3. $93$ $MeV$

  4. $39$ $MeV$

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Correct Option: A
Explanation:

$m=1\ a.m.u.=1.66\times10^{-27}kg$

Its energy equivalent, using $E=mc^2$ is $E=1.49\times10^{-10}\ J$.
or $E=1.49\times10^{-10}/1.6\times10^{-13}\ MeV=931\ MeV$

The binding energy per nucleon of deuteron $ \left( \frac { 2 }{ 1 }  H \right)  $ and helium nucleus $ \left( \frac { 4 }{ 2 } He \right)  $ is.1.1 meV and 7 meV respectively. If two deuteron nuclei react to from s single helium nucleus, then the energy released is:

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. 13.9 MeV

  2. 26.9 MeV

  3. 23.6 MeV

  4. 19.2 MeV

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Correct Option: C

The energy equivalent to a substance of mass $1$g is?

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $18\times 10^{13}$J

  2. $9\times 10^{13}$J

  3. $18\times 10^6$J

  4. $9\times 10^6$J

Show answer
Correct Option: B
Explanation:

$E=mC^2$

$=1\times 10^{-3}\times 9\times 10^{16}$
$=9\times 10^{13}$J

The binding energy expressed in $MeV$ is given for the following nuclear reactions :
$ _2He^3+\ _0n^1\rightarrow\ _2He^4+20\ MeV$
$ _2He^4+\ _0n^1 \rightarrow\ _2He^5 -0.9\ MeV$
Which of the following conclusions are correct ?

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. $ _2He^4$ is less stable than both $ _2He^3$ and $ _2He^5$

  2. $ _2He^4$ is less stable than $ _2He^3$ but more stable than $$ _2He^5$

  3. $ _2He^4$ is less stable than $ _2He^5$ but more stable than $$ _2He^3$

  4. $ _2 He^4$ is more stable than both $ _2He^3$ and $ _2He^5$

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Correct Option: D

An electron and a positron are moving side by side in the positive $x-$direction at $1.5\times 10^8\ m/s$. When they annihilate each other, two photons are produced that move along the $x-$axis, then : 

nuclear reactions nuclear structure nuclei atomic nuclei physics

  1. both move in positive $x-$direction

  2. both move in positive direction along $x-$axis

  3. both may move in same direction

  4. both $(a)$ and $(c)$ are correct

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Correct Option: B