Browse Questions

The distance of a point p from a point source of light $S_1$ is $100. 1243\;cm$ and from another point source $S_2$ is $100.1664\;cm$ Find $(S_2P-S_1P)$ and $(S_2P +S_1P)$ correct upto the same number of significant figures.

$\begin{array}{1 1}(A)\;200\;cm \\(B)\;23 \;cm \\(C)\;98 \;cm \\(D)\;25\;cm \end{array}$

$S_2P- S_1P= 100.1664\;cm -100.1243\;cm$
$\qquad= 0.0421\;cm$
The difference of two length have 3 significant figure. Now
$S_2P +S_1P =100.1664\;cm+100.1243\;cm$
$\qquad= 200.2907\;cm$
Since the number of significant figures in difference is 3, the number of significant figures in sum should also be 3 Thus,
$S_2P+S_1P=200\;cm$
Hence A is the correct answer.