What is the percentage of photosynthetically active radiation (PAR) within incident solar radiation?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 2-10 %
Note: The given answer is as per the official NTA Answer Key. However, none of the given options appears to be correct, because the share of PAR in the incident solar radiation is about 50 per cent (less than 50 per cent), as explained below.
Photosynthetically active radiation (PAR) is the part of sunlight that plants can use in photosynthesis. Of the solar radiation that falls on the Earth, less than 50 per cent is PAR. Plants then capture only 2-10 per cent of this PAR.
(1) 20-40 % — Incorrect. This is not the figure of about 50 per cent for PAR.
(2) 50-70 % — Incorrect. PAR is less than 50 per cent, so a value above 50 per cent cannot be right.
(3) 1-2 % — Incorrect. This is much too small for the share of PAR in sunlight.
(4) 2-10 % — Correct as per NTA; however, it is not the share of PAR in sunlight. It is the part of the PAR that plants capture.
The share of PAR in incident solar radiation is about 50 per cent, and no option gives it.
NCERT Extract:
Energy Flow –
