lo 5 rosalie ho
TRANSCRIPT
14-9,14-10
Created by Rosalie Ho
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
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
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
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
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]
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)
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
Activity
a)Sketch the resultant wave of the following waves
b) Is it constructive or destructive interference?
c)Calculate the resultant amplitude
Question 1
Question 2
Answers Question 1
Answers Question 1
b) Constructive
c) 40m
Answers Question 2
Answers Question 2
b) Destructive
c) 5m