$A$ block of metal is heated to a temperature much higher than the room temperature and allowed to cool in a room free from air currents. Which of the following curves correctly represents the rate of cooling?

If the distance of the point $P(1, -2, 1)$ from the plane $x + 2y - 2z = \alpha$,where $\alpha > 0$,is $5$,then the foot of the perpendicular from $P$ to the plane is:

Solid $NaCl$ is a bad conductor of electricity because

$\lim _{x \rightarrow 0} \frac{\sin x \sin ^{-1} x}{x^2}$ is equal to

In Young's double slit experiment,the $y$-coordinates of the central maximum and the $10^{th}$ maximum are $2\, cm$ and $5\, cm$ respectively. When the $YDSE$ apparatus is immersed in a liquid of refractive index $\mu = 1.5$,what will be the new $y$-coordinates?

Which one of the following statements about packing in solids is incorrect?