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Dispersion of white light by a prism occurs because:
AThe prism absorbs some colours
BThe refractive index of the prism material depends on wavelength — violet refracts most (highest n), red least (lowest n)
CWhite light contains only one wavelength
DAll colours travel at different speeds in air
Answer & Solution
Correct answer: B. The refractive index of the prism material depends on wavelength — violet refracts most (highest n), red least (lowest n)
**Dispersion**: n varies with wavelength → different colours bend by different amounts. **Violet (shortest λ) → highest n → maximum deviation**; **red (longest λ) → lowest n → minimum deviation**. Result: white light splits into a spectrum.
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