Tag: nuclear reactions

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Questions Related to nuclear reactions

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

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

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

  1. a,b

  2. c,d

  3. b,c,d

  4. only d
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

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.

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

Choose the correct statement :

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

$1$ $a.m.u$ is equivalent to 

  1. $931$ $MeV$
  2. $139$ $MeV$
  3. $93$ $MeV$
  4. $39$ $MeV$
Reveal answer Fill a bubble to check yourself
A Correct answer
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 $E=1.49\times10^{-10}/1.6\times10^{-13}\ MeV=931\ MeV$

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

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:

  1. 13.9 MeV

  2. 26.9 MeV

  3. 23.6 MeV

  4. 19.2 MeV
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total binding energy of two deuterons = 2 × 2.2 = 4.4 MeV. Total binding energy of helium = 4 × 7 = 28 MeV. Energy released = 28 - 4.4 = 23.6 MeV. Note: This is another duplicate with 'meV' typo (should be MeV).

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

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 ?

  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$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A positive energy release (Q > 0) indicates a stable product, while a negative energy release (Q < 0) indicates an unstable product. Since the first reaction releases 20 MeV, He-4 is more stable than He-3. Since the second reaction requires 0.9 MeV, He-5 is less stable than He-4.

Multiple choice nuclear reactions nuclear structure nuclei atomic nuclei physics

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 : 

  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
Reveal answer Fill a bubble to check yourself
B Correct answer