Explanation:
Given, \(\theta=0.4 \mathrm{rad}, l=0.25 \mathrm{~m}\) and \(\alpha=0.01\). Specific rotation of sugar solution,
\(\alpha = \frac{{{\rm{Angle}}\,\,\,{\rm{of}}\,\,{\rm{rotation}}}}{{{\rm{Length}}\,\,\,{\rm{of}}\,\,\,{\rm{tube}} \times {\rm{Concentration}}}}\)
\( = \frac{\theta }{{l \times C}}\)
\({\therefore C = \frac{\theta }{{l\alpha }} = \frac{{0.4}}{{0.25 \times 0.01}}}\)
\({ = 160\;kg\;{m^{ - 3}}}\)
Thus, purity of sugar solution
\(=\dfrac{160}{200} \times 100=80 \%\)