Express:
$(a)$ The energy required to break one bond in $DNA$ in $eV$.
$(b)$ The kinetic energy of an air molecule $(10^{-21} \; J)$ in $eV$.
$(c)$ The daily intake of a human adult in kilocalories.

(N/A) The energy required to break one bond of $DNA$ is given by:
$\frac{10^{-20} \; J}{1.6 \times 10^{-19} \; J/eV} \simeq 0.06 \; eV$.
Note: $0.1 \; eV = 100 \; meV$ ($100$ millielectron volt).
$(b)$ The kinetic energy of an air molecule is given by:
$\frac{10^{-21} \; J}{1.6 \times 10^{-19} \; J/eV} \simeq 0.0062 \; eV$.
This is equivalent to $6.2 \; meV$.
$(c)$ The average daily energy intake of a human adult is approximately $10^7 \; J$. Converting this to kilocalories:
$\frac{10^7 \; J}{4.2 \times 10^3 \; J/kcal} \simeq 2400 \; kcal$.