1. Chapter 22 The Energy of Waves Preview Section 1 The Nature of WavesThe Nature of Waves Section 2 Properties of WavesProperties of Waves Section 3 Wave InteractionsWave Interactions Concept Mapping

2. Chapter 22 Section 1 The Nature of Waves Bellringer What do you think of when you hear the word wave? Write a brief description in your science journal of what you think a wave is. Then write a short paragraph describing a time you might have experienced waves.

3. Chapter 22 Objectives Describe how waves transfer energy without transferring matter. Distinguish between waves that require a medium and waves that do not. Explain the difference between transverse and longitudinal waves. Section 1 The Nature of Waves

4. Chapter 22 Wave Energy A wave is any disturbance that transmits energy through matter or empty space. Energy can be carried away from its source by a wave. However, the material through which the wave travels does not move with the energy. Section 1 The Nature of Waves

5. Chapter 22 Section 1 The Nature of Waves

6. Chapter 22 Wave Energy, continued Waves and Work As a wave travels, it does work on everything in its path. The waves in a pond do work on the water to make it move up and down. The waves also do work on anything floating on the water’s surface. The fact that the water and floating objects move tells you that the waves are transferring energy. Section 1 The Nature of Waves

7. Chapter 22 Wave Energy, continued Energy Transfer Through a Medium Most waves transfer energy by the vibration of particles in a medium. A medium is a substance through which a wave can travel. Sound waves, water waves, and seismic waves all need a medium through which to travel. Section 1 The Nature of Waves

8. Chapter 22

9. Wave Energy, continued Energy Transfer Without a Medium Visible light waves, microwaves, radio waves, and X rays are examples of waves can transfer energy without going through a medium. These waves are electromagnetic waves. Although electromagnetic waves do not need a medium, they can go through matter. Section 1 The Nature of Waves

10. Chapter 22 Types of Waves Transverse Waves are waves in which the particles vibrate perpendicularly to the direction the wave is traveling. Transverse waves are made up of crests and troughs. Water waves, waves on a rope, and electromagnetic waves are examples of transverse waves. Section 1 The Nature of Waves

11. Chapter 22 Types of Waves, continued Longitudinal Waves are waves in which the particles vibrate back and forth along the path that the waves moves. Longitudinal waves are made up of compressions and rarefactions. Waves on a spring are longitudinal waves. Section 1 The Nature of Waves

12. Chapter 22 Section 1 The Nature of Waves

13. Chapter 22 Types of Waves, continued Sound Waves are longitudinal waves. Sound waves travel by compressions and rarefactions of air particles, as shown below. Section 1 The Nature of Waves

14. Chapter 22 Types of Waves, continued Combinations of Waves A transverse waves and a longitudinal wave can combine to form a surface wave. Surface waves look like transverse waves, but the particles of the medium move in circles rather than up and down. Section 1 The Nature of Waves

15. Chapter 22 Section 2 Properties of Waves Bellringer Draw a longitudinal wave and a transverse wave in your science journal. Label the parts of each wave.

16. Chapter 22 Objectives Identify and describe four wave properties. Explain how frequency and wavelength are related to the speed of a wave. Section 2 Properties of Waves

17. Chapter 22 Amplitude The amplitude of a wave is the maximum distance that the particles of a medium vibrate from their rest position. A wave with a large amplitude carries more energy than a wave with a small amplitude does. Section 2 Properties of Waves

18. Chapter 22 Wavelength A wavelength is the distance between any point on a wave to an identical point on the next wave. A wave with a shorter wavelength carries more energy than a wave with a longer wavelength does. Section 2 Properties of Waves

19. Chapter 22 Frequency Frequency is the number of waves produced in a given amount of time. Frequency is usually expressed in hertz (Hz). One hertz equals one wave per second. If the amplitudes are equal, high-frequency waves carry more energy than low-frequency waves. Section 2 Properties of Waves

20. Chapter 22 Section 2 Properties of Waves

21. Chapter 22 Wave Speed Wave Speed is the speed at which a wave travels. Wave speed (v) can be calculated using wavelength ( ) and frequency (f), by using the wave equation, which is shown below: v   f Section 2 Properties of Waves

22. Chapter 22 Section 2 Properties of Waves

23. Chapter 22 Wave Speed, continued Frequency and Wavelength Relationship Frequency and wavelength are inversely related. So, if one value is doubled, the other value will be cut in half. The wave speed of a wave in a certain medium is the same no matter what the wavelength is. So, the wavelength and frequency depend on the wave speed, not the other way around. Section 2 Properties of Waves

24. Chapter 22 Characteristics of a Wave Click below to watch the Visual Concept. Visual Concept Section 2 Properties of Waves

25. Chapter 22 Section 3 Wave Interactions Bellringer Write the symbols v, f, and in your science journal. What does each symbol stand for? How does each symbol relate to the other two symbols? Draw a diagram if it helps.

26. Chapter 22 Objectives Describe reflection, refraction, diffraction, and interference. Compare destructive interference with constructive interference. Describe resonance, and give examples. Section 3 Wave Interactions

27. Chapter 22 Reflection Reflection happens when a wave bounces back after hitting a barrier. Light waves reflecting off an object allow you to see that object. A reflected sound wave is called an echo. Waves are not always reflected when they hit a barrier. A wave is transmitted through a substance when it passes through the substance. Section 3 Wave Interactions

28. Chapter 22 Refraction Refraction is the bending of a wave as the wave pass from one medium to another at an angle. When a wave moves from one medium to another, the wave’s speed and wavelength changes. As a result, the wave bends and travels in a new direction. Section 3 Wave Interactions

29. Chapter 22 Refraction, continued Refraction of Different Colors When light waves from the sun pass through a water droplet or a prism, the light is refracted. But the different colors in sunlight are refracted by different amounts, so the light is spread out into its separate colors. Section 3 Wave Interactions

30. Chapter 22 Diffraction Diffraction is the bending of waves around a barrier or through an opening. The amount of diffraction of a wave depends on its wavelength and the size of the barrier or opening the wave encounters. Section 3 Wave Interactions

31. Chapter 22 Interference Interference is the result of two or more waves overlapping. Constructive Interference happens with the crests of one wave overlap with the crests of another wave or waves. The troughs of the waves also overlap. The result is a new wave that has a larger amplitude than the original waves had. Section 3 Wave Interactions

32. Chapter 22 Interference, continued Destructive Interference happens with the crests of one wave and the troughs of another wave overlap. The new wave have a smaller amplitude than the original waves had. When the waves involved in destructive interference have the same amplitude and meet each other at just the right time, the result is no wave at all. Section 3 Wave Interactions

33. Chapter 22 Section 3 Wave Interactions

34. Chapter 22 Interference, continued Standing Waves are waves that appear to be standing still. A standing wave only looks as if it is standing still. Waves are actually going in both directions. In a standing wave, certain parts of the wave are always at the rest position because of total destructive interference. Other parts have a large amplitude because of constructive interference. Section 3 Wave Interactions

35. Chapter 22 Interference, continued The frequencies at which standing waves form are called resonant frequencies. Resonance happens when an object vibrating at or near the resonant frequency of a second object causes the second object to vibrate. An example of resonance is shown on the next slide. Section 3 Wave Interactions

36. Chapter 22 Interference, continued Section 3 Wave Interactions

37. Chapter 22 The Energy of Waves Use the terms below to complete the concept map on the next slide. transverseamplitude frequencyenergy wavesmedium longitudinalwave speed Concept Mapping

38. Chapter 22 The Energy of Waves

39. Chapter 22 The Energy of Waves