8th Grade Science Homework
Due on Friday, 11/30/12
Name_____________________________________
Date__________________Teacher_____________
This week we will…8.8(C) explore how different wavelengths of the electromagnetic spectrum such as
light and radio waves are used to gain information about distances and properties of components in the
universe.
1 As the storm clouds roll out and the last of the rain slowly drips to a stop,
something magical happens. The Sun peeks through the remaining storm
clouds and a beautiful rainbow appears. Its bright vivid colors bend in an
arch through the sky. The band of light that you see shows you the visible
colors of the electromagnetic spectrum. Astronomers, scientists who study
space, use the electromagnetic spectrum to learn about the different
objects in the universe.
2 The electromagnetic spectrum can be defined as the electromagnetic waves that are emitted
from the Sun and other objects in the universe. To better understand the spectrum, it is broken
into smaller categories depending upon wavelength. From the longest to the shortest, the
categories are: radio waves, microwaves, infrared light, visible light, ultraviolet rays, x-rays, and
gamma rays.
3 Radio waves have the longest wavelength in the electromagnetic spectrum. A single
wavelength can span the length of a football field or continue going until they are a mile long.
These types of waves have low frequencies and energy. Radio waves bring music to your ears
or a call to your cell phone. Scientists, however, use radio waves to learn about the composition
of galaxies, stars, comets, and planets. Astronomers use radio telescopes arranged in an array
to collect the waves that are emitted by these astrological objects.
4 Microwaves are the next division on the electromagnetic spectrum. Their wavelengths can
range from less than an inch in length to as long as a foot. You have probably used
microwaves, yourself, to pop some popcorn or heat up your food. Scientists use microwaves a
little differently. These waves can easily pass through different kinds of weather. They are great
for sending images back to Earth from space, even on a cloudy day. Astronomers also use
microwaves to discover information about the structure of our galaxy and galaxies that are close
to us.
5 Infrared light comes after microwaves on the electromagnetic spectrum. The shortest infrared
wavelengths are almost microscopic, while the largest are the size of a pin head. You
experience infrared light every day. The warmth you feel from the Sun, a fire, or a hot metal
slide are examples of heat emitted by infrared light. Some of the shorter infrared waves are
used by remote controlled objects like your television or stereo. Astronomers use infrared light
to map the dust in between stars. They can also take infrared images of Earth to study cloud
structure or ocean temperatures.
6 In the middle of the spectrum is visible light. Think back to the rainbow that appeared after the
storm. The seven colors of light that you see are known as visible light. Visible light is the only
electromagnetic light on the spectrum that you can actually see. Red has the longest
wavelength, and violet has the shortest. When all of the colors are combined, white light is
produced.
7 Ultraviolet light or UV light has a shorter wavelength than visible light. Have you ever been in
the Sun for too long? What happened to your skin? The ultraviolet light emitted from the Sun
probably gave you a painful sunburn. This type of light cannot be seen by your eye alone. By
placing ultraviolet telescopes on satellites, astronomers learn about the structure and evolution
of galaxies.
8 The next electromagnetic wave on the spectrum is x-rays. Hopefully you have never had a
broken bone, but if you have, then you have been exposed to x-rays. X-rays can pass through
your skin but not your bones or teeth. The image produced on the x-ray film will tell the doctor if
and where your bone is broken. Astronomers use x-ray telescopes with x-ray detectors placed
on satellites to study objects in space. The x-ray telescopes cannot be placed on Earth. Earth’s
atmosphere is so thick that it does not allow x-rays to pass through.
9 Gamma rays are the last electromagnetic wave on the spectrum. Having the shortest
wavelength and the most energy, they have the potential to kill cancerous cells. Astronomers
use gamma rays to try to understand how the universe began, its age, and how fast it is
expanding.
10 Through the use of the electromagnetic spectrum, scientists find a vast amount of scientific
information to study. From radio waves to visible light to gamma rays, each wavelength provides
a different answer to the mystery of the universe.
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1. The electromagnetic spectrum can be defined best by —
2. If an astronomer wants to study the composition of planets and stars, the best
wavelength to use is —
3. On the electromagnetic spectrum, the only form of light that we can see is —
4. What kind of information does infrared light waves provide to scientists?
5. ______________has the longest wavelength and_________ has the shortest.