\(1 \sin 60^{\circ}=\frac{4}{3} \sin r \rightarrow \sin r=\frac{3 \sqrt{3}}{8} \rightarrow \tan r=\frac{3 \sqrt{3}}{\sqrt{37}}\)
By the diagram
\(x \sqrt{3}+1.5 \tan r =2.15\)
\(x \sqrt{3}=2.15-1.5 \times \frac{3 \sqrt{3}}{\sqrt{37}}\)
\(x =\frac{2.15}{\sqrt{3}}-\frac{1.5 \times 3}{\sqrt{37}}\)
\(=1.241-0.739\)
\(=0.502\)
\(\approx 0.50 \text { meter }\)
\(x =50\,cm\)
(કાચનો વક્રીભવનાંક = $1.5$ આપેલ છે.)