Infra-red rays increase the temperature of black bodies on absorption, What changes are caused by light rays?

Answer 1

Infrared radiation is popularly known as "heat" or sometimes "heat radiation," since many people attribute all radiant heating to infrared light. This is a widespread misconception, since light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun only accounts for 50%of the heating of the Earth, the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths. Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation. It is true that objects at room temperature will emit radiation mostly concentrated in the 8-12 micron band, but this is not distinct from the emission of visible light by incandescent objects and ultraviolet by even hotter objects (see black body and Wien's displacement law).

Heat is energy in transient form that flows due to temperature difference. Unlike heat transmitted by thermal conduction or thermal convection, radiation can propagate through a vacuum.

The concept of emissivity is important in understanding the infrared emissions of objects. This is a property of a surface which describes how its thermal emissions deviate from the ideal of a blackbody. To further explain, two objects at the same physical temperature will not 'appear' the same temperature in an infrared image if they have differing emissivities.


Black body:

is an object that absorbs all electromagnetic radiation that falls onto it. No radiation passes through it and none is reflected. It is this lack of both transmission and reflection to which the name refers.
http://en.wikipedia.org/wiki/Black_body


Wien's displacement law:

is a law of physics that states that there is an inverse relationship between the wavelength of the peak of the emission of a black body and its temperature.
http://en.wikipedia.org/wiki/Wien's_displacement_law

Answer 2

Any electromagnetic radiation (IR, visible, UV, radio waves, etc.) which are absorbed by a 'black body' cause its temperature to rise.

Doug

Answer 3

infra-red is part of the light spectrum but invisible to the human eye

Answer 4

They also increase the temperature.