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Properties of Waves

Properties of Waves. Let’s Surf!. What is a wave?. A wave is an oscillation that travels, moving energy from one place to another Caused by a vibration The oscillation spreads outward from where it started. Properties of a Wave. A crest is the highest point of the wave.

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Properties of Waves

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  1. Properties of Waves Let’s Surf!

  2. What is a wave? • A wave is an oscillation that travels, moving energy from one place to another • Caused by a vibration • The oscillation spreads outward from where it started.

  3. Properties of a Wave • A crestis the highest point of the wave. • A troughis the lowest point of the wave.

  4. Properties of a Wave • The amplitude, A, of a wave is the maximum height the wave rises above the origin (equilibrium point).

  5. Properties of a Wave • The wave period, P, is the time it takes one wave to pass the observer.

  6. Properties of a Wave • Wavelength is the distance from any point on a wave to the same point on the next cycle of the wave (usually from crest to crest). • Symbol: l Units: meters (m)

  7. Properties of a Wave • The frequency of a wave is the number of waves passing a particular point in one second. • Symbol: ƒ Unit: Hertz (Hz) or s-1

  8. Speed of a Wave • The speed is the distance traveled (one wavelength) divided by the time it takes (one period). Speed = frequency X wavelength v = ƒ·l

  9. Example Calculations: The wavelength of a wave on a string is 1.5 meters and its speed is 5 m/s. Calculate the frequency and the period of the wave.

  10. Review Problems 1. What is the speed of a wave with a frequency of 22 Hz and a wavelength of 6.2 m? 2. Calculate the frequency of a wave traveling at 3.0 x108 m/s with a wavelength of 1.96 x 10-6 m.

  11. Relationship between frequency, wavelength and energy: • There is an inverse relationship between wavelength and frequency. • There is a direct relationship between energy and frequency. • Therefore: • As wavelength increases, both the frequency and energy of the wave decrease. • As wavelength decreases, both the frequency and energy of the wave increases.

  12. What is a wave “pulse”? • A wave pulseis a short ‘burst’ of a traveling wave. • It is sometimes easier to see the motion of wave pulses than it is to see long waves with many oscillations.

  13. Types of Waves: Transverse • A wave whose oscillations are perpendicular to the direction the wave travels. • Examples: Water waves, light waves, S-waves

  14. Types of Waves: Longitudinal • A wave whose oscillations are in the same direction as the wave travels. • aka = compression waves • Examples: Sound waves, P-waves

  15. Standing Waves: • A wave trapped in one spot. • Ex. Guitar string

  16. Four wave interactions • When a wave encounters a surface, four interactions can occur: • reflection • refraction • diffraction • absorption

  17. Examples of Interactions: • Reflection: • Mirror (light), echo (sound) • Refraction: • Eyeglasses, microscope lenses • Diffraction: • Hologram, prism • Absorption: • Sunglasses absorbing UV radiation • Sound proofing a recording studio We see colors due to both absorptionandreflection!

  18. Constructive Interference: • Constructive interference happens when waves add up to make a larger amplitude. • Suppose you make two wave pulses on a stretched string. • One comes from the left and the other comes from the right. • When the waves meet, they combine to make a single large pulse.

  19. Destructive Inference • During destructive interference, waves add up to make a wave with smaller or zero amplitude. • What happens when one pulse is on top of the string and the other is on the bottom? • When the pulses meet in the middle, they cancel each other out.

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