Waves, Light, Sound and Color Waves Transfer energy through matter or space.
Ch. 14: Waves and Energy Transfer
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Transcript of 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):– 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
Examples
• A sound wave is an example of a ________ wave.
• An ocean wave is an example of a _________ wave.
• Earthquake (seismic Wave) = ____
Measuring a Wave• Amplitude = max displacement from rest/
equilibrium
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
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
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
Example Problem pg. 333
• A sound wave has a frequency of 262 Hz and a wavelength measured at 1.29 m.A) What is the speed of the wave?B) How long will it take the wave to travel the
length of a football field, 91.4 m?C) What is the period of the wave?
14.2 Wave Behavior
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.
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)
Superposition of Waves• Interference: the result of 2 or more waves– Constructive: waves add– Destructive: waves cancel (result = 0/ node)
Continuous Waves
• Waves generated as a continuous train of oscillations with a constant frequency and amplitude.
Standing Waves• The combination of 2 waves 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.
Waves in Two Dimensions• Reflection– Law of reflection: the angle of incidence is equal
to the angle of reflection
Waves in Two Dimensions• Refraction– The change in direction of waves at the boundary
between two different media
Diffraction and Interference of Waves• Diffraction:– The spreading of waves around the edges of a
barrier• Ex. Around a coral barrier reef
Wave Interference