The sun emits an electromagnetic spectrum
covering a range of wavelengths including the
visible region as well as the ultraviolet (UV) and
Infrared (IR) regions. So the sun emits light
of every color, but not with equal intensity.
The emission spectrum of the sun (along with other
stars) is described very well by what is called
“blackbody radiation.” In physics a
blackbody is a perfect or “ideal” radiator.
An ideal blackbody will emit a spectrum of
electromagnetic radiation whose intensity at a
given wavelength depends on the temperature of the
object. The temperature of the sun is around
5780 Kelvin. Here, you can see a comparison
between the electromagnetic radiation from the sun
compared to an ideal blackbody radiator at 5778
solar spectrum .
You can see from the figure that the sun emits
electromagnetic radiation across the entire region
of the visible spectrum as well as the UV and
Infrared regions with a peak intensity around
500 nanometers. You can also see that the
Earth’s atmosphere has a large effect on the
electromagnetic radiation that we observe at sea
level. In particular, ozone (O3) in the
atmosphere absorbs UV light, and water vapor in
the atmosphere as well as carbon dioxide absorb
light in the IR region. Additionally, particles in
the atmosphere scatter some of the light through a
Rayleigh scattering , which is the reason
the sky appears blue and the sun appears yellow.
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