alleryStart learning →Over which wavelength range do plant pigment molecules absorb light, a range called photosynthetically active radiation?
AFrom 900 nm to 600 nm
BFrom 700 nm to 400 nm
CFrom 500 nm to 200 nm
DFrom 400 nm to 100 nm
Answer & Solution
Correct answer: B. From 700 nm to 400 nm
1. Pigment molecules can only absorb energies within a narrow band.
2. Plant pigment molecules absorb only light in the wavelength range of 700 nm to 400 nm.
3. Plant physiologists call that range photosynthetically active radiation.
4. Retinal pigments in the human eye see the same band, which is why it is also called visible light.
5. Wavelengths beyond 700 nm carry too little energy to excite an orbital electron.
6. Wavelengths below 400 nm carry so much energy that they bleach the pigment instead.
_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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