(a) Electromagnetic radiation used for water purification: U.V (Ultra Violet) rays.

(b)  Electromagnetic radiation used for eye surgery: Infrared Radiation (Laser light).

Nuclear Fission:

When a heavy nucleus (A > 235 say) breaks into two lighter nuclei (nuclear fission), the binding energy per nucleon increases i.e, nucleons get more tightly bound. This implies that energy would be released in nuclear fission.

Nuclear Fusion:

When two very light nuclei join to form a heavy nucleus, the binding is energy per nucleon of fused heavier nucleus more than the binding energy per nucleon of lighter nuclei, so again energy would be released in nuclear fusion.

Example:${}_{1}H^2 + {}_{1}H^2 \underset{ }{\to } {}_{2}H{e}^4 + 26 Mev$

BE Graph:

A₀  = 100

A_t = 3.125

A_t = A₀.e^-λt

$$\begin{gathered} 3.125 = 100 {\mathrm{e}}^{\frac{-0.693}{10}\mathrm{t}} \\ \frac{3.125}{100} = {\mathrm{e}}^{-0.0693 \mathrm{t}} \\ \frac{100}{3.125} = {\mathrm{e}}^{0.0693 \mathrm{t}} \\ {\log }_{\mathrm{e}} \frac{100}{3.125} = 0.0693 \mathrm{t} \\ {\mathrm{t}}_2 = \frac{2.303 {\log }_{10}^{12}}{0.0693} \\ \mathrm{t} = 50.1 \mathrm{years} \end{gathered}$$

A.

(i) and (iv)

Binding energy per nucleon of each product is less than that of each reactant.