Lo 5 rosalie ho
Transcript of Lo 5 rosalie ho
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14-9,14-10
Created by Rosalie Ho
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14-9 Superposition of waves
Have you ever wondered how you can identify the different instruments playing in a concert at the same time ?
This is because of the Principle of Superposition of Waves
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Principle of Superposition of Waves
The net force at a point= sum of all forces
Resultant displacement of the point=sum of displacement (+/-) of all the waves at that point
Waves don’t affect other waves’ interaction with the medium
Waves passes through each other unaffected
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Terms Resultant Wave
Wave obtained by adding all the component waves
Superposition
Process of adding waves to produce a wave that is the sum of all waves
Interference
2 or more waves combining to produce a resultant wave
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14-10 Interference of Waves
Travelling in the Same direction There are 2 waves
Wave 1 has a phase constant of 0 and wave 2 has a phase constant of Φ
The different of the phases is Φ-0=Φ
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Wave functions of given 2 waves Wave function 1 :D1(x,t)= Asin(kx-ωt)
Wave function 2 :D2(x,t)=Asin(kt-ωt+Φ)
Or
Wave function2:D2(x,t)=Asin[k(x+Φ/k)-ωt]
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Resultant wave
Eqn of resultant wave of wave 1 & 2:
D(x,t)=2Acos(Φ/2)sin(kx-ωt+Φ/2)
Resultant amplitude of resultant wave from wave 1 & 2 = 2Acos(Φ/2)
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Constructive and destructive interference
Constructive : When the phase difference of 2 waves are in a multiple of 2pi rad
Destructive: when the phase difference of 2 waves are in a multiple of pi rad , they will cancel each other out
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Activity
a)Sketch the resultant wave of the following waves
b) Is it constructive or destructive interference?
c)Calculate the resultant amplitude
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Question 1
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Question 2
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Answers Question 1
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Answers Question 1
b) Constructive
c) 40m
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Answers Question 2
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Answers Question 2
b) Destructive
c) 5m