See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Optical Activity and Angle of Rotation **Understanding the concept:** Optical activity is the property of chiral compounds to rotate the plane of polarized light (PPL). The angle of rotation $(\alpha)$ depends on several factors. **Relationship for angle of rotation:** $$\alpha = [\alpha] \times l \times c$$ Where: - $[\alpha]$ = specific rotation (intrinsic property of the compound) - $l$ = length of polarimeter tube (in dm) - $c$ = concentration of solution (in g/ml) **Analysis of given options:** **(a) Concentration:** Directly proportional to $\alpha$ ✓ **(b) Length of polarimeter tube:** Directly proportional to $\alpha$ ✓ **[CORRECT]** **(c) Wavelength of light:** Inversely related; different wavelengths show different rotations ✓ **(d) Temperature:** Affects the optical rotation ✓ **Why option B is the answer:** The length of the polarimeter tube appears explicitly in the fundamental equation relating angle of rotation. A longer tube means the light passes through more of the optically active solution, directly increasing the angle of rotation proportionally. $$\boxed{\text{Option B: Length of polarimeter tube is correct}}$$