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W ave s

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W ave s

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  1. Waves • Objectives: • Learn the traits of mechanical waves • Learn the types of waves that can occur • Calculate and distinguish between speed, wavelength, and frequency of a wave • Differentiate between reflection behavior of waves • Identify what causes the Doppler Effect • Hear and see it in the application of sound and music

  2. Waves Waves transport energywithout transporting material. The material they travel through is called a medium, if the medium changes the wave travels differently. Mechanical Waves require a medium-material-to travel and transfer energy. Electromagnetic waves do not require a medium to travel and transfer energy.

  3. Types of waves Single waves – pulses Periodic waves-One wave after another (wave trains)

  4. More Types of Waves Transverse – the medium vibrates perpendicular to the energy transfer – know the parts. Longitudinal – the medium vibrates parallel to the energy transfer-know the parts

  5. Measuring Wave Properties Period (T)– Time for 1 cycle or for 1 wave to pass. Measured in seconds(s) Frequency (f) – the number of waves per second measured in hertz (hz) Wavelength (ƛ) – The length of one full wave. measured in meters (m) Velocity (v) – The speed of the wave. (m/s) V= ƛf Amplitude – The height of the wave – it is approximately how much energy it carries. (meters)

  6. Measuring Wave Properties Relationship between Period (T) and Frequency (f) T=1/f If the period of the wave you’re measuring is 0.4s what is the frequency of the wave? 2.5hz

  7. Measuring Wave Properties Finding the Energy of a wave E=hf or E=h(c/ƛ) for light-waves (because if E=hf, and V= ƛf, then f=V/ƛ and sub (V/ƛ) into the place of f in the equation E=hf)

  8. Measuring Wave Properties Finding the Energy of a wave E=hfv=ƛf T=1/f Find the Energy of a wave that has a period of 2*10-6 s and a wavelength of 23*10-6 m. Planck’s constant is 6.63*10-34 Js

  9. Video-Doppler Effect

  10. What happens when waves interact? • When they meet they add together and then pass through each other. – Interference • Constructive • Destructive • They reflect off of objects. They hit and bounce – transferring a bit of energy into the substance they hit. • Rigid boundaries • Flexible boundaries http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave2.html http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave3.html http://www.acs.psu.edu/drussell/Demos/reflect/reflect.html

  11. Electromagnetic Waves

  12. Mechanical vs. Electromagnetic • Electromagnetic (EM) waves are 3 dimensional. One part of the wave vibrates in the Y-direction, and the other in a Z-direction, while the wave propagates in the X-dircetion • Mechanical waves vibrate in one dimension. Either Transverse or Longitudinally ------------------

  13. Mechanical vs. Electromagnetic • EM waves do not require a medium to travel. They can move through empty outer space and through materials. • Mechanical waves require a medium so they can travel. Without a medium there is no propogation.

  14. Mechanical vs. Electromagnetic • All EM waves travel at the speed of light; 299,920,000 m/s • For the sake of this class we can round up to 300,000,000 m/s • Mechanical waves travel at a relatively quick speed of 343 m/s in air

  15. Electromagnetic Waves Spectrum

  16. Frequency vs. Wavelength • Wavelength is the physical measurement of 1 full wave-a trough and a crest. • Wavelength and frequency are inversely related since the wave speed is ‘constant’ • Freq. is oscillations per second. • Can be full oscillations per fractions of time • Can be fractions of oscillations per full second of time • #wave cycles/time increment

  17. How Speed, Frequency, Wavelength relate The speed of all EM waves are 300,000,000 m/s so… By knowing the speed of EM waves and frequency of the passing wave we can solve for the unknown wavelength via algebra and the equation, V=λf or vice-versa, known wavelength to find frequency

  18. Calculations V=λf What is the exact f of red light? Sub known values »»» 300,000,000m/s=700nm * f 300,000,000m/s=f 0.0000007 m »»» f=4.286x1014Hz

  19. As one value increases the other decreases.

  20. EM Spectrum Mind-Dump(5 minute presentation) • Is this type of wave high or low energy? Why? • Is exposure harmful? • Where does it fit in the range of EM waves, comparatively? • How does the Doppler-effect affect the perceived frequency? • Give an example or case. • Give the facts and figures of your wave: • f, E, T, v, λ, • Historical BG, interesting stories • 2 minimum kinds of teaching/presentation aid. (pic, vid, slide, demo, etc.) • Most of all, “get lost” and “geek out” in researching your assigned EM range. Even though the reporting is superficial, become an “expert” of your EM range. Impress us with something cool about your wave. • 11 Choices: • Long-waves, AM, FM, TV, Radar, Microwaves, Infrared, Visible light, UV, X-rays, Gamma-rays, White-space • You can research independently and collaborate via your own hackpad page or google docs (include the link on the class homepad), then strategize a teaching method