 Download Download Presentation W ave s

# W ave s

Télécharger la présentation ## W ave s

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
##### Presentation Transcript

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.