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INTERFERENCE OF WAVES Section 9.1. Key Terms  Interference  Principle of Superposition  Constructive Interference  Destructive Interference.

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Presentation on theme: "INTERFERENCE OF WAVES Section 9.1. Key Terms  Interference  Principle of Superposition  Constructive Interference  Destructive Interference."— Presentation transcript:

1 INTERFERENCE OF WAVES Section 9.1

2 Key Terms  Interference  Principle of Superposition  Constructive Interference  Destructive Interference

3 Wave Interference  Remember that waves are the result of particle vibrations.  Particles in a medium are connected by forces.  When a single wave passes a particle, it moves in an oval path.  Allows the wave to travel in a certain direction.  When waves meet, a new wave is generated in a process called interference.  The speeds of the combined wave cancel out and the particles move up and down.

4 Wave Interference Cont’d  The waves pass through each other with no loss of energy.  The direction and energy of each wave are preserved. Once they have passed, their characteristics are unchanged.

5 Principle of Superposition  When two waves meet, the forces of their particles are added together.  If the two waves are in phase, the resulting amplitude will be greater than either of the two individual amplitudes.  If the two waves are out of phase, the resulting amplitude will be less than either of the two individual amplitudes.  Principle of Superposition

6 Constructive Interference  The process of forming a wave with a larger amplitude when two or more waves combine.

7 Constructive Interference

8 Destructive Interference  The process of forming a wave with a smaller amplitude when two or more waves combine

9 Destructive Interference

10 Technology Using Interference of Waves  Noise-cancelling headphones generate a wave that is completely out of phase with the sound waves in the environment.  When the wave is played in the headphones, the destructive interference of the waves, cancels the ambient noise.

11 Applying the Principle of Superposition

12 Practice Problems

13 Summary  The process of generating a new wave when two or more waves meet is called interference.  Vibrating particles in a medium react to the sum of all forces on them. Their motion is caused by the sum total of forces on them.  The principle of superposition states that, when two waves meet, the resulting amplitude is the sum of the individual amplitudes.  Constructive interference occurs when two waves combine and the amplitude of the resulting wave is greater than the amplitudes of all the individual waves.  Destructive interference occurs when two waves combine and the amplitude of the resulting wave is less than at least one of the original amplitudes.  Humans can design technologies to take advantage of wave properties. An example of such a technology is noise-cancelling headphones.

14 Homework  Principle of Superposition Worksheet  Page 419  Questions 1 – 3  Chapter 8 Review Questions  Page  Page , 23-27, 29-43


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