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Waves

Waves. Chapter 10. Wave. A wave is a repeating disturbance or movement that transfers energy through matter or space The matter that waves travel through is called a medium The medium can be a solid, liquid, or a gas. Mechanical Waves.

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Waves

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  1. Waves Chapter 10

  2. Wave • A wave is a repeating disturbance or movement that transfers energy through matter or space • The matter that waves travel through is called a medium • The medium can be a solid, liquid, or a gas

  3. Mechanical Waves • Wave pulse= a single bump or disturbance that travels through a medium • Periodic Wave= a wave that moves up and down at the same rate • Transverse Wave =a wave that vibrates perpendicular to the direction of the wave’s motion • Disturbed in the vertical direction, but the pulse travels horizontally

  4. Mechanical Waves Longitudinal Wave= the disturbance is in the same direction as, or parallel to, the direction of the wave’s motion Surface Wave= a wave that has characteristics of both transverse and longitudinal waves

  5. Types of Mechanical Waves Longitudinal Waves Transverse Waves

  6. Measuring Waves Longitudinal Wave

  7. Measuring Waves Transverse Wave

  8. Measuring Waves • Speed= displacement of the wave peak divided by the time internal • Trough= lowest point • Crest=highest point • Wavelength (λ)= the shortest distance between points where the wave pattern repeats (crest to crest OR trough to trough) • Amplitude (A) = the maximum displacement of the wave from its position of rest, or equilibrium • Depends on how it is generated but NOT its speed

  9. Measuring Waves • Phase= any two points on a wave that are one or more whole wavelengths apart are in phase • Period (T)=the amount of time it takes one wavelength to pass a point, measured in seconds • Frequency (f)= the number of wavelengths that pass a fixed point each second, measured in Hertz (Hz) • A frequency of 19 Hz means that 10 waves passes by every second

  10. EQUATIONS!!!!! • Frequency of a Wave: • f=1/T • Frequency is equal to the reciprocal of the period • Measured in Hertz (Hz) • Wavelength : λ=v/f • Wavelength is equal to the velocity divided by the frequency • Measured in meters (m)

  11. Wave Speed • The speed of a wave depends on the medium in which the wave travels • Wave speed (velocity), wavelength, and frequency are all related • λ=v/f • Wavelength and frequency are indirectly proportional (as one goes up the other goes down) • Wavelength and velocity are directly proportional (as one goes up the other goes up) • Velocity and frequency are directly proportional

  12. Practice Problem • A sound wave has a frequency of 192 Hz and travels the length of a football field, 91.4m, in 0.271 s. • What is the speed of the wave? • What is the wavelength of the wave? • What is the period of the wave? • If the frequency was changed to 442 Hz, what would be the new wavelength and period? • ANS: • v=337m/s • λ= 1.76m • T=.00521 s

  13. Wave Behavior Chapter 10 Section 3

  14. Reflection • Law of reflection: the angle of incidence equals the angle of reflection

  15. Refraction • Refraction: the bending of a wave caused by a change in its speed as it moves from one medium to another • The greater the change in speed is, the more the wave bends

  16. Refraction

  17. Diffraction • Diffraction involves the bending of waves around obstacles. Diffraction can occur with any kind of wave. Diffraction explains why sound can be heard around corners. • Diffraction of waves through a slit • Diffraction of waves around an obstacle

  18. Interference Constructive Interference= When the crest of one wave overlaps the crest of another their individual effects add together to produce a wave of increased amplitude Destructive Interference= When the crest of one wave overlaps the trough of another wave their individual effects are reduced

  19. Standing Wave Standing wave= a wave that remains in a constant position This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions. Animation

  20. Standing Waves • A node is a point along a standing wave where the wave has minimal amplitude • An antinode is a point where the amplitude of the standing wave is a maximum • These occur midway between the nodes.

  21. Resonances in Air Columns • Resonance increases the amplitude of a vibration by repeatedly applying a small external force at the same natural frequency • Resonating air columns intensify sound • Closed-pipe resonator: resonates when its length is an odd number of quarter wavelengths • Open-pipe resonator: resonates when the length is an even number of quarter wavelengths • Strings: resonate similar to open-pipe resonators

  22. SOUND • Chapter 11 • Sound.pptx

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