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A Greenhouse Has An Enclosure That Has A High Transmissivity At Short Wavelengths And A Very Low Transmissivity (almost Opaque) For High Wavelengths. Why Does A Greenhouse Get Warmer Than The Surrounding Air During Clear Days? Will It Have A Similar Effect During Clear Nights? |
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Answer» Solar radiation is skewed towards shorter wavelengths. On a clear DAY the glass of the greenhouse admits a large proportion of the incident radiation. Inside the greenhouse, the various surfaces (plants etc.) reflect the radiation; but the reflected radiation is spectrally DIFFERENT, having more of a high wavelength contribution. THUS the reflected radiation is not transmitted WELL by the glass, and is reflected back into the greenhouse. The INTERIOR heats up due to this trapped radiation. The same effect will not be seen on a clear night, since there is no solar radiation. Solar radiation is skewed towards shorter wavelengths. On a clear day the glass of the greenhouse admits a large proportion of the incident radiation. Inside the greenhouse, the various surfaces (plants etc.) reflect the radiation; but the reflected radiation is spectrally different, having more of a high wavelength contribution. Thus the reflected radiation is not transmitted well by the glass, and is reflected back into the greenhouse. The interior heats up due to this trapped radiation. The same effect will not be seen on a clear night, since there is no solar radiation. |
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