Astronomy, Physics, Spectroscopy

Sunlight Through Clouds of Smoke

I was walking to work earlier today and experienced an interesting phenomenon. I was outside and
was walking out from a shadow cast by a nearby building. Immediately I felt the sensation of heat on
my face but I did not know what it was from.  I looked around and realized that the only possible
source of this heat was the sun.

Usually I would not have to look around to realize that the sun is the primary source of noontime heat
but in this particular case the sun was very dim. I soon noticed that the sun was also intensely red. I
knew immediately that something was up. The sun is never that dim and also that intensely warm,
and it is never that red so far from the horizon. Well, something was up.

Smoke from nearby fires changed the way that I perceived the light coming to me from the sun.  It
made sense that the sun was red, because smoke filters out light rays from the sun that have higher
frequencies.  Because the smoke absorbed most of the higher frequency sunlight, the light that I
saw was tinted red.

The following colors are in order of decreasing frequency (and increasing wavelength): violet, indigo, blue,
green, yellow, orange, and red.

The sun emits electromagnetic radiation in a wide range of frequencies. The “color” that is invisible
to us, but is right below the color red in this spectrum, is infrared light. Infrared light is perceived by
us as heat and because the smoke allowed the lower frequency light to pass through, there was a
disproportionate amount of heat coming from the sun.

The following types of electromagnetic radiation are in order of decreasing frequency: gamma rays, x-rays,
ultraviolet light, visible light, infrared light, microwaves, and radio waves

The sun seemed extraordinarily dim, reddish and hot to me because of this characteristic property
of smoke. A normal cloud that is made up of water vapor will block out the components of
electromagnetic radiation (light), much more uniformly.

Brownian movement: noun
The random movement of microscopic particles suspended in a liquid or gas,
caused by collisions with molecules of the surrounding medium. Responsible for the collisions that
the dispersal of smoke.

Electromagnetic Radiation: noun
Another term for light. Light waves are fluctuations of electric and magnetic
fields in space.

Gamma Rays: noun
Highly penetrating light waves that are emitted by radioactive substances.

Infrared Light: noun
Light waves that correspond to radiated heat.

Microwaves: noun
Light waves that can be used to excite, and heat up water molecules.

Radio Waves: noun
Light waves often used for the wireless transmission of information.

Raleigh Scattering: noun
The scattering of electromagnetic radiation by particles with dimensions much
smaller than the wavelength of the radiation, resulting in angular separation of colors and also
responsible for the reddish color of sunset
and the blue of the sky.

Ultraviolet Light: noun
Light waves visible to some types of animals, responsible for sun burning.

Visible Light: noun
Those light waves that can be perceived by the human eye.

X-Rays: noun
Light waves used for their penetrating power in radiography, radiology, radiotherapy, and
scientific research.
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