Chromatic AberrationHardQuestion 20237
Question
Chromatic aberration in lenses is caused by:
- ASpherical shape of the lens
- BVariation of refractive index with wavelength (dispersion)Correct
- CImpurities in the glass
- DLarge aperture of the lens
Correct answer
Variation of refractive index with wavelength (dispersion)
Explanation
n varies with λ (dispersion) → different colours have different focal lengths → blurred coloured fringes around images. Achromatic doublets (convex + concave lens of different glass types) correct this by making the net dispersion zero while retaining converging power.