All objects radiate energy, but we cannot see all objects in the dark. Why?

Question

We claim that all objects radiate energy by virtue of their temperature and yet we cannot see all objects in the dark. Why not?

score 9 · Accepted Answer · answered Dec 08 '13 at 14:23

The human eye is only capable of perceiving a very limited range of electromagnetic radiation, with wavelengths ~400-800 nanometer. Objects at low temperatures (room temperature) do not emit an appreciable amount of radiation in this range. The fact that we CAN see objects when it's light is due to reflection. For more info, take a look at this wikipedia page

score 6 · Answer 2 · answered Dec 08 '13 at 14:26

Any warm body radiates electromagnetic radiation with a spectrum that depends on the temperature. Above 500 degree centrigrade there is enough radiation in the visible part of the spectrum to be visible but at lower temperatures most of the radiation is at infrared frequencies or lower. Our eyes are not sensitive to infrared radiation so we do not see it.

jinawee · Answer 3 · 2013-12-08T16:01:59.920

3

Cold bodies radiate mostly in the infrared zone (invisible to the human eye), but as the temperature increases the body will emmit higher frequencies with more intensity. So room temperature obects will not be seen due to black body radiation.

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As you can see, hot bodies are visible because they emmit visible light mostly.

edited Dec 08 '13 at 16:01

answered Dec 08 '13 at 14:23

jinawee

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score 0 · Answer 4 · answered Sep 10 '17 at 06:55

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Human eye can sense a particular range of wavelength of em radiation at room temperature most of the objects do not radiate in that particular range .

answered Sep 10 '17 at 06:55

Mubarak ahmad

1

All objects radiate energy, but we cannot see all objects in the dark. Why?

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