Question

Figure shows roughly how the force (F) between two adjacent atoms in a solid varies with separation (r)
(i) OQ is equilibrium separation
(ii) Hooke’s law is obeyed around P
(iii) The potential energy of the atom is the gradient of the graph at all points (iv) The energy to separate the atoms completely is obtained from the area enclosed below the axis of r

• A. (i) and (ii) only
• B. (ii) and (iv) only
• C. (i) and (iii) only
• D. (i), (ii) and (iii) only.

Answer 1

The correct option is B

(ii) and (iv) only

i) Q is not equilibrium because U is not minimum there
ii) $\overrightarrow{F}\propto -\overrightarrow{r}\Rightarrow correct$
iii) Wrong because $\Delta U=-\int fdr$
iv) ${\int }_f=f_0^{\infty }f.dr=dissociationenergy\Rightarrow correct$