If the angular diameter of the Sun is about $30'$ and its distance from the Earth is $1.5 \times 10^{11} \, m$,then the solar diameter is:

Accuracy of measurement of a physical quantity depends on which factors?

What is the approximate dimension (thickness) of a molecule of oleic acid?

Suppose you have taken a dilute solution of oleic acid in such a way that its concentration becomes $0.01 \, cm^3$ of oleic acid per $cm^3$ of the solution. Then you make a thin film of this solution (monomolecular thickness) of area $4 \, cm^2$ by considering $100$ spherical drops of radius $\left(\frac{3}{40 \pi}\right)^{1/3} \times 10^{-3} \, cm$. Then the thickness of the oleic acid layer will be $x \times 10^{-14} \, m$. Where $x$ is ...... .

$A$ man wishes to estimate the distance of a nearby tower from him. He stands at a point $A$ in front of the tower $C$ and spots a very distant object $O$ in line with $AC$. He then walks perpendicular to $AC$ up to $B$,a distance of $100 \; m$,and looks at $O$ and $C$ again. Since $O$ is very distant,the direction $BO$ is practically the same as $AO$; but he finds the line of sight of $C$ shifted from the original line of sight by an angle $\theta = 40^{\circ}$ ($\theta$ is known as 'parallax'). Estimate the distance (in $m$) of the tower $C$ from his original position $A$.

$A$ far-off planet is estimated to be at a distance $D$ from the Earth. If its diametrically opposite extremes subtend an angle $\theta$ at an observatory situated on the Earth,the approximate diameter of the planet is .............