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Physics · 2024 · 3 marks
CBSE 2024 · Region 4 · Set 1 · Q22
(a) Differentiate between nuclear fission and fusion. (b) The fission properties of _94 Pu^239 are very similar to those of _92 U^235. How much…
(a)
Differentiate between nuclear fission and fusion.
(b)
The fission properties of $\displaystyle { }_{94} \mathrm{Pu}^{239}$ are very similar to those of $\displaystyle { }_{92} \mathrm{U}^{235}$. How much energy (in MeV ), is released if all the atoms in $\displaystyle 1$ g of pure $\displaystyle { }_{94} \mathrm{Pu}^{239}$ undergo fission ? The average energy released per fission is $\displaystyle 180$ MeV .
Marking-scheme solution
(a)
In nuclear fission, a heavy nucleus splits into two or more lighter nuclei and energy is released.
In nuclear fusion, lighter nuclei combine together to form a heavy nucleus and a larger amount of energy is released.
(b)
Number of atoms in $\displaystyle 1$ g of $\displaystyle { }_{94} \mathrm{Pu}^{239}$:
$\displaystyle =\frac{6.023 \times 10^{23}}{239}$
$\displaystyle =2.5 \times 10^{21}$
Energy released in fission of $\displaystyle 1$ g of $\displaystyle { }_{94} \mathrm{Pu}^{239}$:
$\displaystyle E=180 \mathrm{MeV} \times 2.5 \times 10^{21}$
$\displaystyle E=4.5 \times 10^{23} \mathrm{MeV}$
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CBSE Class 12 Physics past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.