How do scientists study objects far out in space? Modern astronomers use a variety of telescopes to capture information about the universe. Some of the telescopes are part of orbiting satellites outside the Earth's atmosphere; others are right here on Earth. These telescopes monitor light and/or its relatives, that is, light and other forms of radiation in the electromagnetic spectrum.
For example, radar and radio waves were used to investigate the recent asteroid that passed by the Earth.
To help understand how all this works let's explore the different types of radiation found in the electromagnetic spectrum. We split the activities into two posts because it is rather long. In Part 1 we started an electromagnetic spectrum wall chart, examined waves/wavelengths, and radio waves. Now let's find out more.
Part 2 Electromagnetic spectrum activities:
Because of microwave ovens, microwaves have become a household word. But what are microwaves and how do they work?
Microwaves are a form of electromagnetic radiation with wavelengths shorter than radio waves. They are used for all sorts of things, including remote sensing of weather for forecasting, as well as for monitoring space. Some forms are also used for communications.
In the microwave oven, substances containing water molecules absorb microwave energy and heat up.
This simple experiment from Steve Spangler is sure to get kids excited about microwaves.
Physics in the Microwave at Physics Central explains more and has ideas for "expanding" this experiment.
We can't see infrared radiation with our eyes, but we can sometimes feel it is as heat. Certain snakes, called pit vipers, have organs on their heads that can detect infrared radiation (as a way to find their prey in the dark).
We can see infrared radiation using special cameras. Check out this online infrared photo album Click on "start" in the upper right hand corner to see real infrared photographs. If you click on the special magnifying lens and then move your mouse over the image, you'll see the same photograph in visible light. Look at the footprints. Where did they go in the visible light view?
If you have a Macintosh computer, you can fake an infrared photograph using the program Photo Booth. See if you can figure out how the program achieves this effect.
For more about infrared radiation, see:
- Herschel and his discovery of infrared
- The James Webb Space Telescope will detect infrared.
- Science Buddies has a new infrared telescope project that you can build based on the James Webb Space telescope
- Learn about your TV Remote (infrared signals).
(Image from NASA)
3. Visible Light
- prism or glass of water
Take it outside on a sunny day and create rainbows by separating white light into its component colors. (See related post for more information and activities).
If you don't have a prism, Catch The Waves has a color spectrum interactive you can try online.
Demonstration that light waves are a form of energy:
A radiometer can be used to show that light is a form of energy. Place the radiometer in a sunny window and watch the blades/panels inside spin. Energy is the ability to do work, in this case moving the blades.
You can also convert light energy to heat energy by concentrating it with a magnifying lens. Have you ever burned a piece of paper with just sunlight and a magnifying lens? (Only with adult supervision.)
4. Ultraviolet (UV)
Ultraviolet radiation has a slightly shorter wavelength than visible light. Humans can't see ultraviolet light, but many other animals can, including honey bees and butterflies.
Many flowers have spots we can not see in visible light, but that show under ultraviolet light. Scientists call these spots and patterns "nectar guides" because they are thought to attract bees and other pollinators to the flower.
(Photograph is from Wikimedia Commons.)
a. Obtain or borrow an "black light" (available in many hardware and home supply stores). Black lights produce a type of UV light. Materials, such as florescent posters, glow under a black light. Try out the activities in this glowing chemistry post.
Some items that glow under a black light:
- Did you know that ripe bananas glow blue under certain ultraviolet lights?
- Scorpions glow when you shine a black light on them in the dark.
- Certain minerals also glow under UV.
b. Gather some ultraviolet-sensitive beads (see below for one source) that change colors when expose to ultraviolet radiation. Find out whether you have to be in direct sunlight to be exposed to ultraviolet radiation. (We found that there was enough reflected UV in some shady places to color the beads.)
Saturn's Rings in ultraviolet light (Image from NASA)
Have you ever had an x-ray taken, for example at a dentist's office or if you had a broken bone? X-rays are a form of electromagnetic radiation with a very short wavelength.
X-rays are considered to be "ionizing radiation," which means its energy levels are high enough that when it strikes a molecule it can remove an electron, thus forming an ion. Because of this property, exposure to X-rays should be limited.
6. Gamma rays
Certain gamma rays have the highest level of energy of all the forms of electromagnetic radiation, as well as the shortest wavelength. Here on earth gamma rays are only produced by lightning, radioactive decay of certain radioactive elements, and nuclear explosions. In space they are produced by high-energy events such as supernovas.
Gamma rays are harmful and helpful because they are used to treat certain cancers and to kill bacteria in food.
Light and its relatives in the electromagnetic spectrum have a lot of uses, including investigating space. Have you used any forms of electromagnetic radiation today? Leave a comment and let us know which ones.
Uv Beads are available through science, educational, and toy outlets.
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