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2. Resources Bellringers Chapter Presentation Transparencies Standardized Test Prep Visual Concepts Math Skills

3. Waves Chapter 14 Table of Contents Section 1 Types of Waves Section 2 Characteristics of Waves Section 3 Interactions of Waves

4. Section 1 Types of Waves Chapter 14 Objectives • Recognize that waves transfer energy. • Distinguish between mechanical waves and electromagnetic waves. • Explain the relationship between particle vibration and wave motion. • Distinguish between transverse waves and longitudinal waves.

5. Section 1 Types of Waves Chapter 14 Bellringer • Imagine throwing a rock into a pond or lake. Describe the effect that the rock has on the surface of the water. • When surfing, a person moves just ahead of a wave. Where does the energy come from to move the surfer through the water? • What happens to a string on a guitar or other stringed instrument when it is plucked? • When a musician strikes two cymbals together, the cymbals will begin to vibrate and make music. How does the musician stop the music?

6. Section 1 Types of Waves Chapter 14 What Is a Wave? • Awave is a periodic disturbance in a solid, liquid, or gas as energy is transmitted through a medium. • Waves carry energy through matter or space. • Most waves travel through a medium. • The matter through which a wave travels is called themedium. • Waves that require a medium are calledmechanical waves.

7. Section 1 Types of Waves Chapter 14 Formation and Movement of Ocean Waves

8. Section 1 Types of Waves Chapter 14 What Is a Wave?, continued • Light does not require a medium. • Light waves consist of changing electric and magnetic fields in space. • Light waves are calledelectromagnetic waves. • An electromagnetic waveconsists of oscillating electric and magnetic fields, which radiate outward at the speed of light.

9. Section 1 Types of Waves Chapter 14 Electromagnetic Waves

10. Section 1 Types of Waves Chapter 14 What Is a Wave?, continued • Waves transfer energy. • Energy may spread out as a wave travels. • When sound waves travel in air, the waves spread out in spheres. As they travel outward, the spherical wave fronts get bigger, so the energy in the waves spreads out over a larger area.

11. Section 1 Types of Waves Chapter 14 Tsunami

12. Section 1 Types of Waves Chapter 14 Vibrations and Waves • Waves are related to vibrations. • Most waves are caused by a vibrating object. • Electromagnetic waves may be caused by vibrating charged particles. • In a mechanical wave, the particles in the medium also vibrate as the wave passes through the medium. • Vibrations involve transformations of energy.

13. Section 1 Types of Waves Chapter 14 Wave Model

14. Section 1 Types of Waves Chapter 14 Vibrations and Waves, continued • Whenever a spring is expanded or compressed, it is exerting a force that pushes the mass back almost to the original resting position. • As a result, the mass will continue to bounce up and down. • This type of vibration is calledsimple harmonic motion. • A wave can pass through a series of vibrating objects.

15. Section 1 Types of Waves Chapter 14 Wave Model

16. Section 1 Types of Waves Chapter 14 Vibrations and Waves, continued • If the first mass were not connected to the other masses, it would keep vibrating up and down on its own.However, because it transfers its energy to the second mass, it slows down and then returns to its resting position. • A vibration that fades out as energy is transferred from one object to another is calleddamped harmonic motion. • The motion of particles in a medium is like the motion of masses on springs.

17. Section 1 Types of Waves Chapter 14 Transverse and Longitudinal Waves • Particles in a medium can vibrate either up and down or back and forth. • Waves are often classified by the direction that the particles in the medium move as a wave passes by. • Transverse waves have perpendicular motion. • A transverse wave isa wave in which the particles of the medium move perpendicular to the direction the wave is traveling. • Light waves are transverse waves.

18. Section 1 Types of Waves Chapter 14 Transverse Wave

19. Section 1 Types of Waves Chapter 14 Transverse and Longitudinal Waves • Longitudinal waves have parallel motion. • Alongitudinal wave is a wave in which the particles of the medium vibrate parallel to the direction of wave motion. • Sound waves are longitudinal waves. • In a surface wave, particles move in circles. • Surface waves occur at the boundary between two different mediums, such as between water and air. • The particles move both perpendicularly and parallel to the direction that the wave travels.

20. Section 1 Types of Waves Chapter 14 Longitudinal Wave

21. Section 1 Types of Waves Chapter 14 Water Wave Motion

22. Section 2 Characteristics of Waves Chapter 14 Objectives • Identify the crest, trough, amplitude, and wavelength of a wave. • Define the terms frequency and period. • Solve problems involving wave speed, frequency, and wavelength. • Describe the Doppler effect.

23. Section 2 Characteristics of Waves Chapter 14 Bellringer There are many different types of waves. You may be familiar with the electromagnetic spectrum, which includes radio waves, microwaves, infrared light, visible light, ultraviolet light, X rays, and gamma rays. • Name five common applications of waves in the electromagnetic spectrum, and list the type of wave used in each case. • Lasers are made from accurately focused visible light waves that are produced in phase with each other. Lasers made from visible light waves are often used in surgery to perform delicate procedures and to seal the area being treated. Write a paragraph describing how you think this process works.

24. Section 2 Characteristics of Waves Chapter 14 Wave Properties

25. Section 2 Characteristics of Waves Chapter 14 Wave Properties • An ideal transverse wave has the shape of asine curve. • Waves that have the shape of a sine curveare calledsine waves.

26. Section 2 Characteristics of Waves Chapter 14 Wave Properties, continued • Amplitude measures the amount of particle vibration. • Thecrest is the highest point of atransverse wave. • Thetrough is the lowest point of atransverse wave. • Theamplitude isthe maximum distance that the particles of a wave’s medium vibrate from their rest position.

27. Section 2 Characteristics of Waves Chapter 14 Characteristics of a Wave

28. Section 2 Characteristics of Waves Chapter 14 Wave Properties, continued • A longitudinal wave has compressions and rarefactions. • The crowded areas are calledcompressions. • The stretched-out areas are calledrarefactions. • The amplitude of a longitudinal wave is the maximum deviation from the normal density or pressure of the medium.

29. Section 2 Characteristics of Waves Chapter 14 Wave Properties, continued A. A longitudinal wave has compressions and rarefactions. B. The high and low points of this sine curve correspond to compressions and rarefactions in the spring.

30. Section 2 Characteristics of Waves Chapter 14 Wave Properties, continued • Wavelength measures the distance between two equivalent parts of a wave. • Thewavelength isthe distance from any point on a wave to an identical point on the next wave. • Not all waves have a single wavelength that is easy to measure. • Wavelength is represented by the Greek letter lambda, .

31. Section 2 Characteristics of Waves Chapter 14 Wave Properties, continued • The period measures how long it takes for waves to pass by. • The period isthe time that it takes a complete cycle or wave oscillation to occur. • The period is represented by the symbol T. • Frequency measures the rate of vibrations. • Thefrequency is the number of cycles or vibrations per unit of time. • The symbol for frequency isf. • The SI unit for measuring frequency is hertz.

32. Section 2 Characteristics of Waves Chapter 14 Frequency

33. Section 2 Characteristics of Waves Chapter 14 Wave Period of Ocean Waves

34. Section 2 Characteristics of Waves Chapter 14 Wave Properties, continued • The frequency and period of a wave are related. • The frequency is the inverse of the period.

35. Section 2 Characteristics of Waves Chapter 14 Wave Properties, continued • Light comes in a wide range of frequencies and wavelengths. • Our eyes can detect light with frequencies ranging from about 4.3  1014 Hz to 7.5  1014 Hz. • Light in this range is calledvisible light. • The full range of light at different frequencies and wavelengths is called theelectromagnetic spectrum.

36. Section 2 Characteristics of Waves Chapter 14 Visible Light

37. Section 2 Characteristics of Waves Chapter 14 The Electromagnetic Spectrum

38. Section 2 Characteristics of Waves Chapter 14 Wave Speed • Wave speed equals frequency times wavelength.

39. Section 2 Characteristics of Waves Chapter 14 Equation for the Speed of a Wave

40. Section 2 Characteristics of Waves Chapter 14 Math Skills • Wave Speed The string of a piano that produces the note middle C vibrates with a frequency of 264 Hz. If the sound waves produced by this string have a wavelength in air of 1.30 m, what is the speed of sound in air? • List the given and unknown values. Given:frequency, f = 264 Hz wavelength, = 1.30 m Unknown:wave speed, = ? m/s

41. Section 2 Characteristics of Waves Chapter 14 Math Skills, continued • Write the equation for wave speed. • = f  • Insert the known values into the equation, and solve.  = 264 Hz  1.30 m = 264 s−1  1.30 m  = 343 m/s

42. Section 2 Characteristics of Waves Chapter 14 Wave Speed, continued • The speed of a wave depends on the medium. • In a given medium, though, the speed of waves is constant; it does not depend on the frequency of the wave. • Kinetic theory explains differences in wave speed. • The arrangement of particles in a medium determines how well waves travel through it. • In gases, the molecules are far apart and move around randomly. Waves don’t travel as fast in gases.

43. Section 2 Characteristics of Waves Chapter 14 Wave Speed, continued • In liquids, such as water, the molecules are much closer together. But they are also free to slide past one another. • In a solid, molecules are not only closer together but also tightly bound to each other. Waves travel very quickly through most solids. • Light has a finite speed. • All electromagnetic waves in empty space travel at the same speed, the speed of light, which is • 3.00  108 m/s (186 000 mi/s). • Light travels slower when it has to pass through a medium such as air or water.

44. Section 2 Characteristics of Waves Chapter 14 Doppler Effect • Pitch is determined by the frequency of sound waves. • Thepitch of a sound, how high or low it is, is determined by the frequency at which sound waves strike the eardrum in your ear. • A higher-pitched sound is caused by sound waves of higher frequency. • Frequency changes when the source of waves is moving. • TheDoppler effect is an observed change in the frequency of a wave when the source or observer is moving.

45. Section 2 Characteristics of Waves Chapter 14 Doppler Effect and Sound

46. Section 3 Wave Interactions Chapter 14 Objectives • Describe how waves behave when they meet an obstacle or pass into another medium. • Explain what happens when two waves interfere. • Distinguish between constructive interference and destructive interference. • Explain how standing waves are formed.

47. Section 3 Wave Interactions Chapter 14 Bellringer • The back of a mirror is flat and highly reflective. Describe how you think a mirror works. • Why do you think one piece of safety equipment that backpackers carry into the wilderness is a mirror? • Describe what an echo is. • Blinds in the windows of homes, schools, and offices can be tilted up or down, or they can be closed completely. Explain how varying positions of the blinds controls light.

48. Section 3 Wave Interactions Chapter 14 Reflection, Diffraction, and Refraction • Reflection is the bouncing back of a ray of light, sound, or heat when the ray hits a surface that it does not go through. • Waves reflect at a free boundary. • The reflected wave is exactly like the original wave except that the reflected wave is traveling in the opposite direction to the direction of the original wave. • At a fixed boundary, waves reflect and turn upside down.

49. Section 3 Wave Interactions Chapter 14 Reflection

50. Section 3 Wave Interactions Chapter 14 Reflection