3. Electromagnetic Spectrum Vocabulary transverse wave: electromagnetic wave: a transverse wave that transfers electrical and magnetic energy. electromagnetic energy: energy that is transferred by electromagnetic waves polarized light: Only some light passes through a polarized filter. The light that passes through vibrates in only one direction and is called polarized light. radiation: a process in which energetic particles or energy waves travel through a medium or space medium: a solid, liquid or gas through which waves travel
5. Electromagnetic Spectrum You actually know more about it than you may think! The electromagnetic (EM) spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group. Radiation is energy that travels and spreads out as it goes -- visible light that comes from a lamp in your house and radio waves that come from a radio station are two types of electromagnetic radiation. Other examples of EM radiation are microwaves, infrared and ultraviolet light, X-rays and gamma-rays.
6. Electromagnetic Spectrum Radios, televisions, mobile phones, and radar use signals made up of electromagnetic waves. These are waves that carry energy as electricity and magnetism at the speed of light. Light we can see is also an electromagnetic wave, but other types of electromagnetic waves are invisible. The various types of electromagnetic waves have different frequencies and wavelengths. Together, they make up the electromagnetic spectrum.
7. X-Rays X-RAYS These are high-energy waves that pass through flesh but not bone. In medicine, X-ray photographs are used to check people's bones for damage. In high doses, X-rays can harm people.
8. Gamma Rays Gamma Rays These are produced by radioactivity. They have a short wavelength and a high frequency and carry large amounts of energy. They are very harmful and can cause cancer in humans and animals. (found near nuclear plants, nuclear explosions)
9. Ultraviolet Rays Ultravioliet Rays These invisible waves are slightly shorter than visible violet light and carry more energy. We wear sunglasses and sunscreen to prevent damage to our eyes and skin by ultraviolet rays.
10. Light Rays Visible Light Visible light waves are the only electromagnetic waves we can see. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light.
11. Infrared Rays Infrared Rays Infrared rays are slightly longer waves than visible red light. Although we cannot see infrared, we can feel it as heat. When heat energy is transferred by radiation, it is carried by waves of infrared.
12. Radar/Microwaves Radar waves Radar is a way of locating aeroplanes and ships using a type of radio waves called microwaves. These have much longer wavelengths than visible light. Cooking is another use for microwaves.
13. Radio Waves Radio Waves Radio waves are the longest in the spectrum. They carry radio and TV signals around Earth. Radio waves from outer space are picked up by radio telescopes and used in studies of the universe.
14. Is light an electromagnetic wave? Yes. It’s one of the electromagnetic waves we can see. polarized light:light waves that vibrate in one direction unpolarized light: light waves that vibrate in all directions Some sunglasses are polarizing filters.
15. Polarized Light Polarized Light: The light that passes through a polarized filter vibrating in only one direction.
16. Polarized Filters – Only transmit light waves that are vibrating in a certain direction Experiment with filters, placing them behind each other. Use the flash light shine through one filter shine through both filters see if you can shine the light through both and block out all the light Answer these questions on your own paper. Why does the light appear dimmer through the filter? Why are two filters needed to block out all the light?
17. Draw a diagram to show how light waves are affected by one polarizing filter. Draw a diagram to show how light waves are affected by two polarizing filters together.
19. Familiar things: The microwave you use to heat your food and the cell phones you use are part of the Electromagnetic Spectrum. The light that our eyes can see is also part of the electromagnetic spectrum. Waves in the electromagnetic spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom.
Editor's Notes
Why does light appear dimmer through the filter? (only some of the light is transmitted)Why are two filters needed to block out all the light? (The first filter blocks all the light waves in one direction. The second filter is needed to block the remaining waves.)
