IIT-JEE 2008 · Paper 1 · Physics Q31

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PhysicsMultiple correct+4 / -1Question 31 of 69

Assume that the nuclear binding energy per nucleon (B/A) versus mass number (A) is as shown in the figure. Use this plot to choose the correct choice(s) given below.

Step plot of B/A (MeV) against mass number A: B/A = 2 for A < 100, jumps to 8 for 100 < A < 200, then drops to 4 for A > 200 (to about 260).

Fusion of two nuclei with mass numbers lying in the range of

1<A<50

will release energy

Fusion of two nuclei with mass numbers lying in the range of

51<A<100

will release energy

Fission of a nucleus lying in the mass range of

100<A<200

will release energy when broken into two equal fragments

Fission of a nucleus lying in the mass range of

200<A<260

will release energy when broken into two equal fragments

Answer and worked solution

Official answer: B, D

Energy is released when the products have a larger binding energy per nucleon than the reactants (total $A$ unchanged).

(A) Two nuclei with $A<50$ fuse to $A<100$ : B/A stays 2. No energy.
(B) Two nuclei with $51<A<100$ fuse to $102<A<200$ : B/A rises from 2 to 8. Energy released.
(C) $100<A<200$ split into halves with $A<100$ : B/A falls from 8 to 2. Energy absorbed.
(D) $200<A<260$ split into halves with $100<A<130$ : B/A rises from 4 to 8. Energy released.

(B), (D)

Topics:Mass defect and binding energy Nuclear fission and fusion

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IIT-JEE 2008 · Paper 1, Physics question 31