What is a moderator? Name the material used as a moderator in a nuclear reactor.

What was the fissionable material used in the bomb dropped at Nagasaki (Japan) in the year $1945$?

Choose the correct option to complete the net effect of the fusion reaction that occurs in the Sun: $4_1^1H + 2e^- \rightarrow$ . . . . . . $+ 2\nu + 6\gamma +$ . . . . . .

The binding energy per nucleon of ${}_3^7Li$ and ${}_2^4He$ nuclei are $5.60 \, MeV$ and $7.06 \, MeV$, respectively. In the nuclear reaction ${}_3^7Li + {}_1^1H \to 2 \, {}_2^4He + Q$, the value of energy $Q$ released is ............ $MeV$.

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:
$(A)$ Fusion of two nuclei with mass numbers lying in the range of $1 < A < 100$ will release energy.
$(B)$ Fusion of two nuclei with mass numbers lying in the range of $100 < A < 200$ will release energy.
$(C)$ Fission of a nucleus lying in the mass range of $100 < A < 200$ will release energy when broken into two equal fragments.
$(D)$ Fission of a nucleus lying in the mass range of $200 < A < 260$ will release energy when broken into two equal fragments.

In the proton-proton cycle in the Sun,the energy released when an electron and its antiparticle combine is $\qquad$ .