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# Interference

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1. Section 3 Wave Interactions Chapter 14 Interference • Waves in the same place combine to produce a single wave. • Interference is the combination of two or more waves of the same frequency that results in a single wave. • The resulting wave can be found by adding the height of the waves at each point. • Crests are considered positive, and troughs are considered negative. • This method of adding waves is sometimes known as theprinciple of superposition.

2. Section 3 Wave Interactions Chapter 14 Constructive and Destructive Interference

3. Section 3 Wave Interactions Chapter 14 Interference, continued • Constructive interference increases amplitude. • Constructive interference is any interference in which waves combine so that the resulting wave is bigger than the original waves. • The amplitude of the resulting wave is the sum of the amplitudes of the two individual waves. • Destructive interference decreases amplitude. • Destructive interference is any interference in which waves combine so that the resulting wave is smaller than the largest of the original waves. • When destructive interference occurs between two waves that have the same amplitude, the waves may completely cancel each other out.

4. Section 3 Wave Interactions Chapter 14 Interference, continued • Interference of light waves creates colorful displays. • Interference of sound waves produces beats. • When two waves of slightly different frequencies interfere with each other, they produce beats.

5. Section 3 Wave Interactions Chapter 14 Standing Waves • Interference can cause standing waves. • A standing waveisa pattern of vibration that simulates a wave that is standing still. • Standing waves can form when a wave is reflected at the boundary of a medium. • Although it appears as if the wave is standing still, in reality waves are traveling in both directions.

6. Section 3 Wave Interactions Chapter 14 Standing Wave

7. Section 3 Wave Interactions Chapter 14 Standing Waves, continued • Standing waves have nodes and antinodes. • Each loop of a standing wave is separated from the next loop by points that have no vibration, callednodes. • Nodes lie at the points where the crests of the original waves meet the troughs of the reflected waves, causing complete destructive interference. • Midway between the nodes lie points of maximum vibration, calledantinodes. • Antinodes form where the crests of the original waves line up with the crests of the reflected waves, causing complete constructive interference.

8. Section 3 Wave Interactions Chapter 14 Standing Waves, continued • Standing waves can have only certain wavelengths. • In general, standing waves can exist whenever a multiple of half-wavelengths will fit exactly in the length of the string. • It is possible for standing waves of more than one wavelength to exist on a string at the same time.

9. Section 3 Wave Interactions Chapter 14 Concept Mapping

10. Standardized Test Prep Chapter 14 Understanding Concepts 1. Which of the following waves can be transmitted without a medium? A. electromagnetic B. longitudinal C. mechanical D. transverse

11. Standardized Test Prep Chapter 14 Understanding Concepts 1. Which of the following waves can be transmitted without a medium? A. electromagnetic B. longitudinal C. mechanical D. transverse

12. Standardized Test Prep Chapter 14 Understanding Concepts 2. How do longitudinal waves carry energy from a source? F. Particles vibrate outward from the source of the wave. G. Particles vibrate parallel to the direction of the wave. H. Particles vibrate perpendicular to the direction of the wave. I. Particles vibrate both parallel and perpendicular to the direction of the wave.

13. Standardized Test Prep Chapter 14 Understanding Concepts 2. How do longitudinal waves carry energy from a source? F. Particles vibrate outward from the source of the wave. G. Particles vibrate parallel to the direction of the wave. H. Particles vibrate perpendicular to the direction of the wave. I. Particles vibrate both parallel and perpendicular to the direction of the wave.

14. Standardized Test Prep Chapter 14 Understanding Concepts 3. What is measured by the amplitude of a wave? A. the amount of vibration of particles B. the direction of vibration of particles C. the rate of vibration of particles D. the wavelength of vibration of particles

15. Standardized Test Prep Chapter 14 Understanding Concepts 3. What is measured by the amplitude of a wave? A. the amount of vibration of particles B. the direction of vibration of particles C. the rate of vibration of particles D. the wavelength of vibration of particles

16. Standardized Test Prep Chapter 14 Understanding Concepts 4. Which combination of wave interactions can cause a standing wave? F. diffraction and interference G. diffraction and reflection H. reflection and interference I. reflection and refraction

17. Standardized Test Prep Chapter 14 Understanding Concepts 4. Which combination of wave interactions can cause a standing wave? F. diffraction and interference G. diffraction and reflection H. reflection and interference I. reflection and refraction

18. Standardized Test Prep Chapter 14 Understanding Concepts 5. Why do astronauts on the moon need a radio transmitter to carry on a conversation with each other?

19. Standardized Test Prep Chapter 14 Understanding Concepts 5. Why do astronauts on the moon need a radio transmitter to carry on a conversation with each other? Answer: Sound waves require a medium to carry energy from one place to another. On the moon, there is no air to carry the vibrations.

20. Standardized Test Prep Chapter 14 Reading Skills The Doppler Effect applies to light as well as sound. Astronomers have used this fact to measure the speed of objects in space as they move away from Earth. They know the frequency and wavelength of the light as it leaves a star because the energy transitions in atoms are the same throughout the universe. When the light reaches Earth, it has a different frequency from when it left the star. 6. Assess how the knowledge that light always travels at the same speed is essential for determining the speed at which a distant galaxy and Earth are moving apart.

21. Standardized Test Prep Chapter 14 Reading Skills 6. Assess how the knowledge that light always travels at the same speed is essential for determining the speed at which a distant galaxy and Earth are moving apart. Answer: Using the change in frequency of light and the fact that the speed of light is constant, astronomers can calculate how fast the objects are moving away from one another.

22. Standardized Test Prep Chapter 14 Reading Skills The Doppler Effect applies to light as well as sound. Astronomers have used this fact to measure the speed of objects in space as they move away from Earth. They know the frequency and wavelength of the light as it leaves a star because the energy transitions in atoms are the same throughout the universe. When the light reaches Earth, it has a different frequency from when it left the star. 7. Astronomers have observed that the wavelength of light reaching Earth from one edge of the sun is slightly different than from the other edge. What can be concluded about the sun based on this observation?

23. Standardized Test Prep Chapter 14 Reading Skills 7. Astronomers have observed that the wavelength of light reaching Earth from one edge of the sun is slightly different than from the other edge. What can be concluded about the sun based on this observation? Answer: The observation indicates that the sun is rotating. The light from one edge is shifted to a shorter wavelength, and light from the other edge is shifted to a longer wavelength.

24. Standardized Test Prep Chapter 14 Interpreting Graphics 8. What wave phenomenon is demonstrated in this illustration? A. diffraction C. reflection B. Interference D. refraction

25. Standardized Test Prep Chapter 14 Interpreting Graphics 8. What wave phenomenon is demonstrated in this illustration? A. diffraction C. reflection B. Interference D. refraction

26. Standardized Test Prep Chapter 14 Interpreting Graphics 9. Which of the points on the illustration indicates an antinode? F. W H. Y G. X I. Z

27. Standardized Test Prep Chapter 14 Interpreting Graphics 9. Which of the points on the illustration indicates an antinode? F. W H. Y G. X I. Z