Question

When wet air and dry air is put in 2 seperate beakers with a blackened brass discs which re-emits visible light absorbed in the form of infrared radiation and I shine a lamp for 10 minutes the temperature is almost the same in both the beakers. Could you please explain why?

Answer 1

Visible light absorbed in the form of infrared radiation has frequencies which correspond with the natural    frequencies of vibration of the carbon dioxide, methane, water and ozone molecules. These molecules absorb the radiation and re-emit it in all directions. The net effect is that the atmosphere effectively traps some of the sun’s energy and prevents the earth from cooling rapidly at night.

Wet air is dense than dry air. Hot bodies are better emitters than cool ones and cool bodies are better absorbers than hot ones. Hence dry air better re-emits visible light absorbed in the form of infrared radiation (consider stratosphere where gases are almost in dry form - very less moisture or humidity ot wet air).

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