Which wavelengths do carotenoids absorb, and which do they reflect?
AThey absorb green and reflect blue, red and violet
BThey absorb violet and reflect green, blue and red
CThey absorb blue and reflect yellow, red and orange
DThey absorb red and reflect blue, green and violet
Answer & Solution
Correct answer: C. They absorb blue and reflect yellow, red and orange
1. Carotenoids absorb in the short-wavelength blue region.
2. They reflect the longer yellow, red and orange wavelengths.
3. Reflecting those longer wavelengths is why carrots and orange peel look orange.
4. A pigment always shows the colours it fails to absorb, so the reflected set must be the visible one.
5. An answer with red absorbed would make a carotenoid look blue-green, which contradicts what is seen.
6. Chlorophyll is the pigment that fails to absorb green, so putting green in the absorbed column swaps the two classes.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 8 "Photosynthesis", section 8.2 The Light-Dependent Reactions of Photosynthesis_
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