Electromagnetic waves presentationss.ppt
- 2. The Electromagnetic Spectrum The Electromagnetic Spectrum The EM spectrum is the ENTIRE range of EM waves in The EM spectrum is the ENTIRE range of EM waves in order of increasing frequency and decreasing wavelength. order of increasing frequency and decreasing wavelength. As you go from As you go from left left right right, the , the wavelengths get smaller wavelengths get smaller and the and the frequencies get higher frequencies get higher. This is an . This is an inverse inverse relationship relationship between wave between wave size and frequency. size and frequency. (As one goes up, the other goes down.) (As one goes up, the other goes down.) This is because the This is because the speed of ALL EM waves is the speed of light (300,000 km/s). speed of ALL EM waves is the speed of light (300,000 km/s).
- 3. Things to Remember Things to Remember The higher the frequency, the more energy the The higher the frequency, the more energy the wave has. wave has. EM waves EM waves do not require media do not require media in which to travel in which to travel or move. or move. EM waves are considered to be EM waves are considered to be transverse waves transverse waves because they are made of vibrating electric and because they are made of vibrating electric and magnetic fields at right angles to each other, and to magnetic fields at right angles to each other, and to the direction the waves are traveling. the direction the waves are traveling. Inverse relationship between wave size and frequency: as wavelengths get smaller, frequencies get higher.
- 4. Radio waves Radio waves: Have the longest wavelengths and : Have the longest wavelengths and the lowest frequencies; wavelengths range the lowest frequencies; wavelengths range from 1000s of meters to .001 m from 1000s of meters to .001 m Used in: RADAR, cooking food, satellite Used in: RADAR, cooking food, satellite transmissions transmissions The Waves (in order…) The Waves (in order…)
- 5. Infrared waves Infrared waves (heat): Have a shorter wavelength, (heat): Have a shorter wavelength, from .001 m to 700 nm, and therefore, a higher from .001 m to 700 nm, and therefore, a higher frequency. frequency. Used for finding people in the dark and in TV Used for finding people in the dark and in TV remote control devices remote control devices Visible light Visible light: Wavelengths range from 700 nm (red : Wavelengths range from 700 nm (red light) to 30 nm (violet light) with frequencies light) to 30 nm (violet light) with frequencies higher than infrared waves. higher than infrared waves. These are the waves in the These are the waves in the EM spectrum that humans EM spectrum that humans can see. can see. Visible light waves are a very Visible light waves are a very small part of the EM spectrum! small part of the EM spectrum!
- 6. ROY G. BV ROY G. BV red red orange orange yellow yellow green green blue blue violet violet Visible Light Visible Light Remembering the Order Remembering the Order
- 7. Ultraviolet Light Ultraviolet Light: Wavelengths : Wavelengths range from 400 nm to 10 nm; the frequency (and therefore the energy) is high enough with UV rays to penetrate living cells and cause them damage. Although we cannot see UV light, bees, bats, butterflies, some small rodents and birds can. UV on our skin produces vitamin D in our bodies. Too much UV can lead to sunburn and skin cancer. UV rays are easily blocked by clothing. Used for sterilization because they kill bacteria.
- 8. X-Rays X-Rays: Wavelengths from 10 nm to .001 nm. : Wavelengths from 10 nm to .001 nm. These rays have enough energy to penetrate These rays have enough energy to penetrate deep into tissues and cause damage to cells; deep into tissues and cause damage to cells; are stopped by dense materials, such as bone. are stopped by dense materials, such as bone. Used to look at solid structures, such as bones and Used to look at solid structures, such as bones and bridges (for cracks), and for treatment of cancer. bridges (for cracks), and for treatment of cancer.
- 9. Gamma Rays Gamma Rays: Carry the most energy and have : Carry the most energy and have the shortest wavelengths, less than one the shortest wavelengths, less than one trillionth of a meter (10 trillionth of a meter (10-12 -12 ). ). Gamma rays have enough energy to go through Gamma rays have enough energy to go through most materials easily; you would need a 3-4 ft thick most materials easily; you would need a 3-4 ft thick concrete wall to stop them! concrete wall to stop them! Gamma rays are released Gamma rays are released by nuclear reactions in by nuclear reactions in nuclear power plants, by nuclear power plants, by nuclear bombs, and by nuclear bombs, and by naturally occurring naturally occurring elements on Earth. elements on Earth. Sometimes used in the Sometimes used in the treatment of cancers. treatment of cancers.
- 10. Gamma Rays Gamma Rays This picture is a This picture is a “scintigram” “scintigram” It shows an asthmatic It shows an asthmatic person’s lungs. person’s lungs. The patient was given a slightly radioactive gas to The patient was given a slightly radioactive gas to breath, and the picture was taken using a gamma breath, and the picture was taken using a gamma camera to detect the radiation. camera to detect the radiation. The colors show the air flow in the lungs. The colors show the air flow in the lungs.
- 11. Micro Worlds, Lawrence Berkeley National Laboratory. http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html Image Sources Image Sources NASA http://spaceplace.nasa.gov/blue-sky/ NASA http://science-edu.larc.nasa.gov/EDDOCS/Wavelengths_for_ Colors.html NASA http://missionscience.nasa.gov/ems/11_xrays.html Andy Darvill, Broadoak Community School, Radioactivity Uses http://www.northallertoncoll.org.uk/science/Additional%20Physics/ Nuclear/Nuclear/Radioactivity/uses.htm 2004 Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399 USA.
Editor's Notes
- #1: Presentation for lesson 4: Exploring the Electromagnetic Spectrum, in the Waves: The Three Color Mystery unit The slides are animated so you can click (space bar, mouse, etc.) to show the next item when the class is ready.
- #3: Play an interactive tutorial to explore the classical representation of an electromagnetic wave as a sine function; you can vary amplitude and wavelength to demonstrate how this function appears in three dimensions. (requires java plug-in) See: http://micro.magnet.fsu.edu/primer/java/electromagnetic/index.html
- #6: Light from the sun looks white, but it is really made up of all the colors of the rainbow. A prism is a specially shaped crystal. When white light shines through a prism, the light is separated into all its colors.