Q21: The instrument used for measuring photosynthetically active radiation (PAR) is: - Principles of Agronomy, Crop Ecology, Geography & Agricultural Meteorology - ICAR AIEEA PG Agronomy 14 July 2023 (Shift 1) Paper | Agrigyan

Radiation measurement instruments in agro-meteorology:

• Line quantum sensor: Specifically designed with calibrated photodiode arrays to measure Photosynthetically Active Radiation ($400-700\text{ nm}$) photon flux density ($\mu\text{mol}\cdot\text{m}^{-2}\cdot\text{s}^{-1}$) within crop canopies.
• Pyranometer: Measures total global solar radiation (direct + diffuse).
• Pyrheliometer: Measures direct beam solar radiation at normal incidence.
• Campbell-Stokes recorder: Records bright sunshine duration hours.