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Why do telescopes built entirely from curved mirrors avoid the chromatic aberration problem that lens-based telescopes must correct for?
AReflection is independent of wavelength, unlike refraction in a lens
BMirrors absorb every wavelength equally before reflecting the rest
CMirrors are always coated to block coloured light entirely
DMirrors have no focal point, so no colour can miss it
Answer & Solution
Correct answer: A. Reflection is independent of wavelength, unlike refraction in a lens
1. Chromatic aberration in lenses comes from the index of refraction changing with wavelength.
2. The law of reflection, which governs mirrors, is independent of wavelength altogether.
3. Because there is no wavelength dependence in reflection, mirrors do not suffer from chromatic aberration the way lenses do.
4. Absorbing colour or blocking light entirely would defeat the purpose of a telescope mirror, so those options do not fit.
_Source: OpenStax Physics (CC BY 4.0), Ch 16 "Mirrors and Lenses", section 16.3 Lenses_
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