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WAVES

WAVES. THE ELECTROMAGNETIC SPECTRUM. Waves are a method that enrgy uses to travel from one location to another. Waves are the result of a vibration traveling from one location to another. velocity. Wave. Energy input (vibration). Types of Waves.

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WAVES

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  1. WAVES THE ELECTROMAGNETIC SPECTRUM

  2. Waves are a method that enrgy uses to travel from one location to another Waves are the result of a vibration traveling from one location to another. velocity Wave Energy input (vibration)

  3. Types of Waves • Longitudinal or compression – vibrate parallel to velocity. ex. Sound • Transverse – vibrations perpendicular to velocity. ex. Light and water waves

  4. Frequency (f) in Hertz (Waves per Second) Wavelength (λ) in meters Crest Amplitude Vertical displacement 1 Hertz .r 1 second Trough λ 2 Hertz f 3 Hertz

  5. Period and Frequency of Vibrations • period – time (seconds) it takes for 1 vibration (wave) to occur. • frequency – number of vibrations (waves) in a second • f = 1/p AND p = 1/f 10Hz has a period of 1/10th of a second Unit: s Unit: Hz or s-1

  6. .1s .3s .5s .7s .9s .2s .4s .6s .8s 1s 1 second Period = 1/10 or 0.1 f = 10 Hz

  7. High Energy Low Energy Electromagnetic Spectrum R O Y G B I V Wavelength (λ) in meters 10-8 104 10-14 10-12 10-10 10-6 10-4 10-2 100 102 Gamma rays Ultraviolet Infrared Radio Microwave X rays TV, FM AM 1010 1022 1020 1018 1016 1014 1012 108 106 104 Frequency (f) in Hertz

  8. Electromagnetic Spectrum

  9. Wave Uses

  10. Relative Wavelength

  11. What type of wave is it? • f = 1.52E22 Hz • f = 3.99E8 Hz • λ = 8.34E-10 m • f = 2.76E10 Hz Use EM spectrum • λ = 2.90E-8 m • f = 6.35E6 Hz • λ = 7.01E-6 m • λ = 9.40E-14 m

  12. Calculating frequency, wavelength, period and velocity

  13. Speed of Light Speed of light (c) in a vacuum = 3.00E8meters per second (m/s) In any other medium you have to calculate velocity v=fλ Vacuum Water

  14. c/λ f = c/f λ = What is the wavelength?What is the frequency?What is the speed of the wave? • The wavelength of an x-ray is 4.32E-11 m. What is its frequency? • Ultraviolet radiation from the sun has a frequency of 2.49E16 Hz. What is its wavelength? • An infrared ray has a frequency of 1.01E10 Hz and a wavelength of 2.95E-2 m. What is the speed of the wave? 3.00E8 m/s 4.32E-11 m 6.94 E18 Hz = = 3.00E8 m/s 2.49E16 s-1 1.20 E-8 m = = 2.98 E8 m/s 1.01E10 Hz x 2.95E-2 m =

  15. Radio Stations • Radio stations transmit their signal in megahertz (MHz) • 1 megahertz = ? Hertz • 106 98.5 MHz 106 Hz 9.85 E7 Hz x = 1 1 MHz

  16. Radio Station’s Wavelength What is the wavelength of these popular radio stations? • 97.9 MHz (you have to convert to Hz first) • 104.5 MHz • 105.3 MHz λ = c/f 3.06 m 9.79E7 Hz λ = c/f 2.87 m 1.045E8 Hz λ = c/f 2.85 m 1.053E8 Hz

  17. Going around the world 7.5 times a second How fast is the speed of light?

  18. Interference • Interference occurs when 2 waves occupy the same space at the same time. • It can be “destructive” or “constructive”, depending if the waves are “in phase” or “out of phase”.

  19. Interference • Destructive • Constructive = + + =

  20. v=fλ Faster =  f or ↓ λ Slower = ↓f or  λ In a vacuum v = (c) speed of light In any other medium you have to calculate velocity

  21. Color Wavelengths

  22. Baaaaaaa! Lambda!

  23. A B C D 2 Hertz λ f 3 Hertz

  24. 1 sec

  25. 1 sec

  26. 1 sec

  27. 1 sec

  28. Title Period (time 1 swing) Mass 1 Mass 3 Mass 4 Mass 2

  29. Title 3 Period (time 1 swing) s No breaks! 0 0 0.25 m 0.75 m 1.00 m 1.00 m 0.50 m String length (m)

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