Electromagnetic Spectrum

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Electromagnetic Spectrum The Speed of Light
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Light allows us to have a meaningful
interaction with our world.
We can see our surroundings when visible light
reflects off objects and into our eyes.
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Light travels from the sun to the earth at
the speed of light. (300 000 km/s)
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There is nothing faster than the speed of light.
(except for spacecrafts in science fiction movies)
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Light is made up of different types of waves or
radiation.
visible light - needed to see and for
photosynthesis
infrared radiation - needed to heat the earth
UV radiation - can cause cancer
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Radiowaves have a longest wavelength, visible
light has a medium wavelength and gamma rays
have the shortest wavelength.
All types of light waves from the sun are
arranged by size and displayed on the
electromagnetic spectrum.
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It is impossible to see other forms of outside of
visible light range of the electromagnetic
spectrum with the naked eye.
For example, special goggles are needed to see
infrared radiation or heat.
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Advances in space technology (non-optical
telescopes and observatories) allow us to see
light from regions of the EM spectrum that would
otherwise be invisible to the human eye.
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A variety of images can be captured by looking at
radiation that is given off from a planet or star
in different areas of the electromagnetic
spectrum outside the visible light range.
visible light only image that can be seen with
naked eye
ultraviolet radiation
radiowaves
infrared radiation
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This information has lead us to support theories
such as The Big Bang Expanding Universe.
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What can we see from our vantage point in the
solar system?
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We can see all objects whose light has had time
to reach us.
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The suns energy does not travel to the earth
immediately. The farther away an object is, the
longer the light takes. It takes about 8 minutes
for the suns solar radiation to reach the
earths surface after leaving the sun.
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When we see the light either from a very distant
star or galaxy, we see the object as it appeared
a very long ago.
Therefore, looking far out in space is like
looking back in time.
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How do we know what the universe looked like 5
billion years ago? We look back 5 billion light
years!
But what does this mean?
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The speed of light is 300,000,000 m/s and has the
symbol c.
Since speed (v) means distance (d) divided by
time( t), the equation for speed is v d/t.
This means that in one second light travels
300,000,000 m.

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Therefore, light travels 9.46 x 10 km in one
light year.
It can range from energy waves in the x-ray
region all the way to the gamma ray region of the
electromagnetic spectrum.
Our human eye can only see the visible region of
the electromagnetic spectrum.
However new technologies (observatories and
telescopes) detect energy emitted from the
universe within wavelengths of the entire
spectrum.
These advances allow humans to see the unseen!