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WAVES

WAVES. W aves difference with oscillation. W aves that travel within or with a medium. As a wave propagates, it carries energy. The energy in light waves from the sun warms the surface of our planet; the energy in seismic waves can crack our planet's crust.

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WAVES

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  1. WAVES Waves difference with oscillation • Waves that travel within or with a medium. As a wave propagates, it carries energy.The energy in light waves from the sun warms the surface of ourplanet; the energy in seismic waves can crack our planet's crust. • Vibration is toing move about the equilibrium position. www.themegallery.com

  2. Reflection Refraction Interference Wave’s contidition difraction Polarization

  3. Mechanical Waves, waves that travel with some material called a medium. Mechanical Waves • Sound waves in gas, • Sound waves in liquid • Sound waves in solid • String waves Waves category Electromagnetic waves can propagate even in empty space, where there is no medium. Electromagnetic waves • Radio waves • light • gelombang radio • gelombang TV

  4. The displacements of the medium are perpendicular or transverse to the direction of travel of the wave along the medium, this is called a transverse wave. Transverse wave • Electromagnetic waves • Repples on a pond • String waves waves Longitudinal wave The motions of the particles of the medium are back and forth along the same direction that the wave travels. We call this a longitudinal wave. • Sounds Wave • Springs wave

  5. The wavelength () is the minimum distance between any two identicalpoints (such as the crests) on adjacent waves The period (T) is thetime required for two identical points (such as the crests) of adjacent wavesto pass by a point. The frequency of a periodic wave (f) is the number of crests (or troughs, or any other point on the wave) that pass a givenpoint in a unit time interval. The maximum displacement of a particle of themedium is called the amplitude (A) of the wave.

  6. Wave number (rad/m), k = 2/ • Angular frequency (rad/dt), =2 / = 2 v/  = 2 f • v = f • v = /k

  7. That is, the traveling sinusoidal wave moves to the right a distance vt in the time t, with amplitude A (m), frequencyf (Hz.),wavelength (m), andwave speed v (m/s) as shown in Figure) a. t = 0 X b. t =  X v  c. t = 2  X 2 v 

  8. If the wave moves to the rightwith a speed v, then the wave function at some later time t is : If the wave moves to the left with a speed v, then the wave function at some later time t is : generally express the wave function in the form,

  9. The wave function can be express When the vertical displacement y is’n zero at x=0 and t=0 Wave phase, isphase constant.

  10. The combination of separate waves in the same region of space to produce aresultant wave is called interference Y1(x,t) = A sin (kx-t) Y2(x,t) = A sin (kx+ t) Y(x,t) = A sin (kx-t) + A sin (kx+ t) Remember, sin α + sin β = 2 sin ½(α+ β) cos ½(α-β) Y(x,t) = 2A sin ½ (kx-t+ kx+ t) cos ½(kx-t- kx- t) Y(x,t) = 2A sin kx cos t = Asw sin kx cos t standing wave on a string, fixed end at x = 0 The standing wave amplitude Asw is twice the amplitude A of either of the original traveling waves: Asw = 2A

  11. EXAMPLE 1 A sinusoidal wave traveling in the positive x direction has anamplitude of 15.0 cm, a wavelength of 40.0 cm, and a frequency of 8.00 Hz. The vertical displacement of the mediumat x=0 and t=0 is also 15.0 cm, as shown in Figure.(a) Find the angular wave number k, period T, angular frequency, and speed v of the wave.(b) Determine the phase constant, and write a generalexpression for the wave function.

  12. Because A = 15 cm and because y = 15 cmat x=0 and t=0 substitution into Equation

  13. By inspection, we can see that the wave function must havethis form, noting that the cosine function has the same shapeas the sine function displaced by 90°. Substituting the valuesfor A, k, and into this expression, we obtain

  14. The speed of a wave (v) traveling on a taut string of mass per unit length  andtension T is

  15. The intensity I at any distance r is therefore inversely proportional to r2 average power, sinusoidal wave on a string

  16. The Doppler Effect

  17. a Stationary Source d =  b Source moves to the right vs  ds = vs T

  18.  =Distance between two adjacent wave front. vs= speed of source, T =time = period, First wave front was move as far as d = v T, or  = v T v = Speed of wave sound on the air At the same time, source have traveled with distance ds = vs T. Hence, the new wave length :  = d - ds =  - vs T =  - vs / v =  (1- vs / v) www.themegallery.com

  19. When a source move toward a stationary observer, frequency heart by observer is: For a source moving with a speed Vsaway a stationary observer,

  20. Doppler effect also happen, when a source is motionless and an observer is moving. • Wave speed relative to the observer is change. • If the observer move toward a stationary source, Wave speed relative to observer is: • v= v + vp , • v = Sound speed in air • Vp=Speed of observer. • So:

  21. because = v/f, so: Generally rule,

  22. Contoh Soal 2 As an ambulance travels east down a highway at a speed of33.5 m/s, its siren emits sound at a frequency of400 Hz. What frequency is heard by a person in a car travelingwest at 24.6 m/s (a) as the car approaches the ambulance and (b) as the car moves away from the ambulance? Solution a) Solution b)

  23. what happens when the speed vS of a source or speed of an observer equalwith the wavespeed v? what happens when the speed vS of a source exceeds the wavespeed v? If an observer toward a source, frequency heart by observer is zero. If a source toward an observer, frequency heart by observer is unlimited. (shock waves) Human’s earonly can heart sound with frequency between 20-20.000 Hz.

  24. If the speed vS of a source exceeds the wavespeed v, happen shock waves and produce sonic boom. The shock wave carries a great dealof energy concentrated on the surface of the cone, with correspondingly great pressure variations. Such shock waves are unpleasant to hear and can cause damage tobuildings when aircraft fly supersonically at low altitudes.

  25. If the medium is not stationary

  26. Contoh Soal 3 Sebuah kereta api yang mendekati sebuah bukit dengan kelajuan 40 km/jam membunyikan peluit dengan frekuensi 580 Hz ketika kereta berjarak 1 km dari bukit. Angin dengan kelajuan 40 km/jam bertiup searah dengan gerak kereta. Tentukan frekuensi yang didengar oleh seorang pengamat di atas bukit. Cepat rambat bunyi di udara adalah 1200 km/jam Tentukan jarak dari bukit di mana gema dari bukit didengar oleh masinis kereta. Berapa frekuensi bunyi yang didengar oleh masinis tersebut?

  27. Jawab: C A B 1 - x 1 - x x 1 km Frekuensi yang didengar oleh pengamat di bukit Misalkan masinis mendengar gema peluit kereta oleh dinding bukit ketika berjarak x km dari bukit. Waktu tempuh kereta dari A ke B adalah

  28. Waktu bunyi merambat dari A ke C kemudian dipantulkan ke B adalah Waktu keduanya sama, maka Frekuensi pantul yang didengar oleh masinis

  29. SEKIAN TERIMAKASIH

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