Refractive Index
Refractive index tells us how much a medium slows down light compared with vacuum or air, and how strongly it bends light.
Practice This ConceptMain explanation
Teacher explanation
A higher refractive index usually means light travels slower in that medium. For a given pair of media, refractive index also tells us how much the ray bends at the boundary. In school problems, refractive index is often found using c/v or sin i / sin r.
Example
If light travels at 2 x 10^8 m/s in glass, the refractive index of glass is 1.5.
Simple analogy
Higher n means slower light and stronger bending.
Common confusion
Students mix up refractive index with density alone. A denser-looking medium is not always the one with the highest optical density.
Exam tip
Use the formula given in the question: c/v for speed problems, or sin i/sin r for angle problems.
Answer writing and exam use
1-mark use
Write the exact meaning of refractive index in one clean line.
2-mark use
Define refractive index and add one example or condition.
3-mark use
Explain refractive index, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
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