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Electromagnetic Waves

Electromagnetic Waves. 8-6.8 Compare the wavelength and energy of waves in various parts of the electromagnetic spectrum (visible light, infrared, and ultraviolet radiation). Important Facts about Electromagnetic Waves. Wide range of wavelengths

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Electromagnetic Waves

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  1. Electromagnetic Waves 8-6.8 Compare the wavelength and energy of waves in various parts of the electromagnetic spectrum (visible light, infrared, and ultraviolet radiation).

  2. Important Facts about Electromagnetic Waves • Wide range of wavelengths • The entire range of wavelengths is called the electromagnetic spectrum. • As energy gets greater: • wavelength gets shorter • frequency increases

  3. The Electromagnetic Spectrum

  4. The Electromagnetic Spectrum

  5. Infrared Radiation • Has longer wavelengths than RED wavelengths of visible light. • Has lower energy than visible light. • ALL objects emit (give off) infrared radiation. • Hotter objects emit more • Thermal energy is transmitted by infrared radiation. • If an object absorbs infrared radiation, it becomes warmer. • “infra”- stem means under/below

  6. Humans, at normal body temperature, radiate most strongly in the infrared at a wavelength of about 10 microns. • (A micron is the term commonly used in astronomy for a micrometer or one millionth of a meter.) • This image shows a man holding up a lighted match! • Which parts of this image do you think have the warmest temperature? • How does the temperature of this man's glasses compare to the temperature of his hand?

  7. Shorter, near infrared waves are not hot at all - in fact you cannot even feel them. These shorter wavelengths are the ones used by your TV's remote control. • Infrared light is even used to heat food sometimes - special lamps that emit thermal infrared waves are often used in fast food restaurants!

  8. This is an image of Phoenix, Arizona showing the near infrared data collected by the Landsat 5 satellite. The light areas are areas with high reflectance of near infrared waves. The dark areas show little reflectance. What do you think the black grid lines in the lower right of this image represent? This image shows the infrared data (appearing as red) composited with visible light data at the blue and green wavelengths. If near infrared is reflected off of healthy vegetation, what do you think the red square shaped areas are in the lower left of the image?

  9. Humans may not be able to see infrared light, but did you know that snakes in the pit viper family, like rattlesnakes, have sensory "pits", which are used to image infrared light? • This allows the snake to detect warm blooded animals, even in dark burrows! • Snakes with 2 sensory pits are even thought to have some depth perception in the infrared!

  10. The image at the left shows a cat in the infrared. • The orange areas are the warmest and the white-blue areas are the coldest. • This image gives us a different view of a familiar animal as well as information that we could not get from a visible light picture.

  11. Visible Light • Can be detected by the human eye • Wavelengths and energy are in the middle of the electromagnetic spectrum • The eye reacts to different wavelengths and energies….that is why we see different colors. • ROY G BIV • is the acronym for the order of colors • Longer wavelengths; Lower energy; Lower frequency: Red • Shorter wavelengths; Higher energy; Higher frequency: Violet

  12. Why is violet always bent/refracted the most? Violet- higher energy = higher frequency = more refraction

  13. Ultraviolet Radiation • Smaller wavelengths and higher energy than violet wavelengths of visible light • UV radiation exposure: • Too much is damaging  skin cancer • Need some exposure to allow our body to produce Vitamin D • “ultra-” means extra

  14. Practical Uses of UV • Black Light • Authenticate passports, licenses, money • Fluorescent Lamps • Spectroscopy • Minerals (GFP) • Sterilization

  15. Minerals under UV (black light)

  16. Ultraviolet (UV) light has shorter wavelengths than visible light. Though these waves are invisible to the human eye, some insects, like bumblebees, can see them!

  17. Diagram of HUT Viewing stars from a distance.

  18. UV’s Effects on Human Body • Minor effects on skin • Cancer • Eye problems • Cataracts seen left • (+) Vitamin D

  19. Science@NASA: EMS (Episode 1) - An Introduction To The Electromagnetic Spectrum • EMS Spectrum • http://www.youtube.com/watch?v=cfXzwh3KadE&feature=related • Infrared • http://www.youtube.com/watch?v=i8caGm9Fmh0 • Stop at 2 min • Ultraviolet • http://www.youtube.com/watch?v=QW5zeVy8aE0 • Visible Light • http://www.youtube.com/watch?v=PMtC34pzKGc • 5:20 min • 5:22 • 3:40 • 4:50

  20. Electromagnetic Spectrum • http://www.youtube.com/watch?v=kfS5Qn0wn2o • 2:15 min

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