NEET UG PHYSICS MCQ: WAVE OPTICS

Specific rotation of sugar solution is $\mathrm{0}\mathrm{.5}\;\mathrm{deg}\;{\mathrm{m}^2}\;\mathrm{k}/\mathrm{g}\mathrm{.}\;200\;\mathrm{kg}{\mathrm{m}^{ - 3}}$  of impure sugar solution is taken in a sample polarimeter tube of length $20\;c\mathrm{m}$ and optical rotation is found to be $19^\circ$. The percentage of purity of sugar is