Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our...
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Transcript of Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our...
![Page 1: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/1.jpg)
Light and the Electro-
magnetic Spectrum
![Page 2: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/2.jpg)
Light and the Electromagnetic Spectrum
• Almost all of our information on the heavens is derived from the light we see
• We have returned samples from the Moon and a comet – Also obtained meteor samples
• We have landed (with unmanned probes) on only a handful of planets and moons
![Page 3: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/3.jpg)
EM Spectrum in Astronomy
• If we could only observe in visible light, our knowledge of the universe would be greatly limited
• By looking at objects at different wavelengths, we get a different view and lots more information
• Some objects are only visible at certain wavelengths
![Page 4: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/4.jpg)
Objects in space that emit
different frequencies on
the EM Spectrum
![Page 5: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/5.jpg)
The Electromagnetic Spectrum• Human eyes are only able
to process information from the visible part of the spectrum
• Toward longer wavelengths, the spectrum includes infrared light, microwaves, and radio
• Toward shorter wavelengths, the spectrum includes ultraviolet light, X-rays, and gamma rays
• All of these are forms of electromagnetic radiation
![Page 6: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/6.jpg)
Wavelength• The distance from one wave crest to the
next
• Radio waves have longest wavelength and Gamma rays have shortest!
![Page 7: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/7.jpg)
What do we mean by wavelength?Light as a Wave
• One way to think about light is as a traveling wave
• A wave is just a disturbance in some medium (water, air, space)
• A wave travels through a medium but does not transport material
• A wave can carry both energy and information
![Page 8: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/8.jpg)
Wave Terminology
• Wavelength - distance between two like points on the wave• Amplitude - the height of the wave compared to undisturbed state
• Period - the amount of time required for one wavelength to pass• Frequency - the number of waves passing in a given amount of time
![Page 9: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/9.jpg)
Wave Relationships
• Note that light is always traveling at the same speed (c ~ 3 x 108 m/s, or 300,000 m/s, or 186,000 miles/sec, or 7 times around the earth in 1 second!)
– Remember: velocity = wavelength x frequency• If frequency increases, wavelength decreases• If frequency decreases, wavelength increases
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Wavelength Units
• Meters: More commonly in nanometers (1 nm = 10-9 meters)
• Angstroms still used– Named for Swedish Astronomer who first
named these wavelengths– 1 nanometer = 10 Ao
![Page 11: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/11.jpg)
Wavelengths of Light - Visible
• What we see as white light is actually made up of a continuum of components
• Traditionally, we break white light into red, orange, yellow, green, blue, indigo, and violet (ROY G BIV)
• There is actually a continuous transition of color, each with its own wavelength and frequency
![Page 12: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/12.jpg)
![Page 13: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/13.jpg)
![Page 14: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/14.jpg)
Bright Line Spectra
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Doppler Effect
• The motion of an object can be measured through a change in the frequency of the waves emitted by the object
• The increase in pitch of an approaching police car is caused by the compression of the sound wave– The pitch decreases as the police car moves away
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![Page 17: Light and the Electro- magnetic Spectrum. Light and the Electromagnetic Spectrum Almost all of our information on the heavens is derived from the light.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649ea25503460f94ba6897/html5/thumbnails/17.jpg)
Doppler Shift
• In astronomy, the same effect happens to light waves
• A source that is moving away will appear redder (redshift)
• A source that is moving toward us will appear bluer (blueshift)
• Note: Only objects moving toward or away from us (radial motion) will show this effect
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Which spectrum (spectra) indicates an object is moving towards earth?
Which spectrum (spectra) indicates an object is moving away from earth?