Hi! I'm Emerald Robinson
 and this "What is?" video
we're going to take a closer look 
at the electromagnetic spectrum.
What we see as light is only a small part
of the electromagnetic spectrum.
The electromagnetic spectrum 
refers to the many types of radiation
released from stars,
 including our own Sun.
Electromagnetic radiation
 travels in waves.
Frequency describes how many waves
 per second a wavelength produces.
Wavelength measures the length
 of an individual wave in meters.
Scientists describe the 
electromagnetic spectrum as a long line.
At one end lie radio waves with
 the longest wavelengths and
lowest frequencies
 in the spectrum.
A single radio wave has the
 length of a football field.
After radio waves come microwaves 
which produce more energy due to
shorter wavelengths and 
higher frequencies.
Cell phones, radar, and 
microwave ovens use microwaves.
Next comes infrared light.
The sun, fire, living creatures and other 
heat sources all produce infrared light.
While we cannot see infrared light, 
we feel it as heat.
Visible light occupies a narrow slice
of the electromagnetic spectrum
nestled between infrared 
and ultraviolet light.
Red wavelengths have 
the lowest frequencies
and longest wavelengths
of visible light.
As you move from red through orange, 
yellow, green, blue and finally violet,
wavelengths shorten
and frequencies increase.
From visible violet light,
we move into ultraviolet frequencies.
Human skin produces Vitamin D
when exposed to ultraviolet light,
but excessive ultraviolet light
 causes sunburns.
Next, X-rays, which pass
 through soft tissue,
but not denser materials such as bone,
making them valuable for medical tests.
X-rays also have security applications
such as airport baggage checks.
Gamma rays produce 
even shorter wavelengths,
higher frequencies
 and more energy.
In comparison to the football field-sized 
wavelengths of radio waves,
gamma-ray wavelengths 
are as small as Adam nuclei.
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