Sunday 31 December 2017

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


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



Answer



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



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