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Ch. 14: Waves and Energy Transfer

Ch. 14: Waves and Energy Transfer. 14.1: Wave Properties. Mechanical Waves. Transverse Waves (Secondary waves or S waves): Wave that travels perpendicular to the direction of motion In an earthquake these arrive second Longitudinal Waves (Primary waves or P waves):

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Ch. 14: Waves and Energy Transfer

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  1. Ch. 14: Waves and Energy Transfer 14.1: Wave Properties

  2. Mechanical Waves • Transverse Waves (Secondary waves or S waves): • Wave that travels perpendicular to the direction of motion • In an earthquake these arrive second • Longitudinal Waves (Primary waves or P waves): • Wave that travels parallel or in the same direction as the motion • In an earthquake, these arrive first • Surface Waves (Rayleigh and Love waves): • Both travel like transverse waves but they are perpendicular to one another • Most dangerous waves in an earthquake

  3. Examples • A sound wave is an example of a ________ wave. • An ocean wave is an example of a _________ wave. • Earthquake (seismic Wave) = ____

  4. Measuring a Wave • Amplitude = max displacement from rest/ equilibrium

  5. Measuring a Wave • Wavelength (λ) = distance between points where the wave pattern repeats itself (usually in meters) • Crest to crest or trough to trough • Speed = distance wave travels/ time V= Δd/Δt

  6. Measuring a Wave • Period (T) = the time (in seconds) it takes for a point (p) to return to its initial position • Frequency = the number of complete oscillations it makes each second… • To calculate frequency (f) = 1/T = 1/ (sec) = Hz • Both apply only to continuous waves

  7. Measuring a Wave • Wavelength, speed, period and frequency • Velocity (V)= m/s = Wavelength (λ) / Period (T) IF: Frequency =1/T T= 1/f Simplifying: • V = λ/T λ/ (1/f) • SO: V =λf • V=wavelength * frequency

  8. Example Problem pg. 333 • A sound wave has a frequency of 262 Hz and a wavelength measured at 1.29 m. • What is the speed of the wave? • How long will it take the wave to travel the length of a football field, 91.4 m? • What is the period of the wave?

  9. 14.2 Wave Behavior

  10. Waves at Boundaries • Incident wave: wave that strikes the boundary • Reflected wave: the returning wave • If the reflected wave is from a less dense medium it will be reflected in the same manner • If the reflected wave is from a more dense medium it will be inverted from its original position.

  11. Superposition of Waves • Principal of Superposition: The displacement of two or more waves overlapping, is the algebraic sum of the individual waves. • Interference: the result of 2 or more waves • Destructive: waves add • Constructive: waves cancel (result = 0/ node)

  12. Superposition of Waves • Interference: the result of 2 or more waves • Constructive: waves add • Destructive: waves cancel (result = 0/ node)

  13. Continuous Waves • Waves generated as a continuous train of oscillations with a constant frequency and amplitude.

  14. Standing Waves • The combination of2waves of equal frequency and intensity travelling in opposite directions. • There are usually 2 displacements: One where the maximum amplitude occurs at the same points as other minimum value of the amplitude of the other.

  15. Waves in Two Dimensions • Reflection • Law of reflection: the angle of incidence is equal to the angle of reflection

  16. Waves in Two Dimensions • Refraction • The change in direction of waves at the boundary between two different media

  17. Diffraction and Interference of Waves • Diffraction: • The spreading of waves around the edges of a barrier • Ex. Around a coral barrier reef

  18. Wave Interference

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