Question detail
How do optical isomers differ in their interaction with plane-polarised light?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Optical isomerism (A-level only)
Question
- A. They rotate light in the same direction
- B. They do not affect light at all
- C. They rotate light in opposite directions
- D. They absorb light equally
Answer
They rotate light in opposite directions
Explanation
Optical isomers differ in their interaction with plane-polarised light because they are chiral and exist as non-superimposable mirror images. This chirality leads to a mechanism where one isomer rotates the light in one direction (clockwise) while the other rotates it in the opposite direction (counterclockwise). The consequence is that this property is used to distinguish between the isomers in various applications, including pharmaceuticals.
Common mistake
Misunderstanding Optical Activity
Students often think that all organic molecules can rotate plane-polarised light, regardless of their structure.
Understand that only chiral molecules, which have a non-superimposable mirror image, can rotate plane-polarised light due to their specific spatial arrangement of atoms.
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