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InterviewSolution
| 1. |
How much photosynthetically active radiation is received by plants from the sun? |
| Answer» The total radiation from the sun coming at the upper boundary of the atmosphere is `1,360 Wm^(-2)` or watts per square meter (the solar constant). 1W is equal to 1 joule per second (joule is the SI unit of energy). This irradiance includes ultraviolet and infrared wavelenths Of this, only about 900 W `m^(-2)` reach plants because the rest is absorbed or scattered by water vapour, dust, `CO_(2)` and ozone present in the atmosphere. Of this, about half is in the infrared, roughly 5 percent is in the ultraviolet, and the rest has wavelengths between 400 to 700 nm. Therefore, the plants receive about 400 to 500 `W m^(-2)`. photosynthetically active radiation from the sun. | |