Chapter 12: Waves

1. Chapter 12:Waves Section 12.1: Waves Section 12.2: Waves in Motion Section 12.3: Natural Frequency and Resonance

2. Content Standard 3:Interaction of Energy and Matter Energy, such as potential, kinetic, and field, interacts with matter and is transferred during these interactions. 1. All energy can be considered to be kinetic energy, which is energy of motion, potential energy, which depends on relative position; or energy contained by a field, such as electromagnetic waves. 2. Waves, includes sounds and seismic waves, waves over water, and light waves, have energy and can transfer energy when they interact with matter (such as used in telescope, solar power, and telecommunication technology)

3. Learning goals and VocabularyPage 194 Information on page 194 will be the responsibility of the student to read and have knowledge in order to succeed on the content exam.

4. Section 12.1: WavesPage 195 Why learn about waves? Waves carry oscillations from one place to another Refer to Figure 12.1 page 195 – ball in water Waves carry information and energy Waves are used to carry information and energy over great distances.

5. Section 12.1: WavesPage 196 Why learn about waves? Continued… Waves are all around us. Refer to the examples on top of page 196 How do you recognize a wave? Students must know this list on pg. 196 Where can we find waves? Refer to pg. 196 – bottom of page.

6. Section 12.1: WavesPage 197 Transverse and longitudinal waves Waves spread through connections A string is continuous because it is connected to itself Transverse waves Has its oscillations perpendicular to the direction the wave moves

9. Section 12.1: WavesPage 197 – continued ….. Transverse and longitudinal waves Longitudinal waves Has oscillations in the same direction as the waves moves. Also known as a compression wave. Sound waves are good example of longitudinal waves.

12. Section 12.1: WavesPage 198 Frequency, amplitudes and wavelength Basic properties Frequency Frequency is measured in Hz Amplitude Wavelength Speed The speed of a wave

13. Section 12.1: WavesPage 198 : Basic Properties Basic properties Waves have cycles, frequency and amplitude which were from chapter 11.1. A new property will be the wavelength.

14. Section 12.1: WavesPage 198 : Frequency Frequency Is the measure how often the wave goes up and down (Fig. 12.5) To measure the frequency, look at one place as the waves passes through. A wave carries its frequency to every area it reaches.

15. Section 12.1: WavesPage 198 : Frequency (Hz) Frequency is measured in Hz. Is the measure how often the wave goes up and down (Fig. 12.5) To measure the frequency, look at one place as the waves passes through. A wave carries its frequency to every area it reaches.

16. Section 12.1: WavesPage 198 : Amplitude Amplitude Learn some terms: Crest: highest part of a wave Trough: lowest part of a wave Line of origin: when a crest/trough is not present Amplitude: 2 amplitudes per cycle – refer to diagram drawn by instructor

17. Section 12.1: WavesPage 198 : Wavelength (m.) Wavelength Is the length of one complete cycle of a wave (Figure 12.7) The symbol “lambda” is used while the meter is the unit. Crest-to-crest or trough-trough.

18. Section 12.1: WavesPage 199 : Speed (m/s) Speed Describes how fast the wave can transmit an oscillation from one place to another. Refer to page 199 and the Skill Sheet for more information.

19. Section 12.1: Waves Page 199 : What is the speed of a wave? What is the speed of a wave? The speed of the wave is different from the speed of whatever the wave is causing to move. Read the last sentence of the 2nd paragraph on page 199

20. Section 12.1: Waves Page 199 : Speed is frequency times wavelength Speed is frequency times wavelength In one complete cycle, a wave moves forward one wavelength. v = f λ Speed = frequency times wavelength Meters/second = Hertz times meters Refer to page 199 and Skill Sheet for further information.

21. Section 12.2 Waves in Motionpage 200 Wave shapes Crest, troughs, and wave fronts Crest - shape of the high points of the wave Troughs – the low points of the wave Wave fronts – crest is sometime referred to as a wave front

22. Section 12.2 Waves in Motionpage 200 Wave shapes Plane waves and circular waves Plane waves – wave fronts that look like straight lines. Wave is started by disturbing the water in a line. Circular waves – wave fronts that appear circular. Wave is started by disturbing the water at a single point.

23. Section 12.2 Waves in Motionpage 200 Wave shapes Determining the direction the wave moves Direction is determined by the shape: Plane waves have straight lines that move perpendicular to the wave fronts. Circular waves have circular wave fronts that move outward from the center.

24. Section 12.2 Waves in Motionpage 201 What happens when a wave hits something? The four wave interactions Reflection Refraction Diffraction Absorption

25. Section 12.2 Waves in Motionpage 201 What happens when a wave hits something? Boundaries Waves are affected by boundaries where conditions change either crossing or at the boundary.

26. Section 12.2 Waves in Motionpage 201 What happens when a wave hits something? Reflection – refer to page 201 for more examples When a wave bounces off an obstacle and travel in another direction. Happens at a boundary (edge) where the wave has to pass from one condition to another.

28. Section 12.2 Waves in Motionpage 202 What happens when a wave hits something? Refraction The wave starts in one direction and changes direction as it crosses a boundary. Remember the pencil in the glass of water. Pencil appears to bend which is due to the fact of the light changing from medium to another.

30. Section 12.2 Waves in Motionpage 201 What happens when a wave hits something? Absorption The wave can be absorbed and disappear. Absorption is what happens when the amplitude of a wave gets smaller and smaller as it passes through a material.

32. Section 12.2 Waves in Motionpage 202 What happens when a wave hits something? Diffraction Waves can bend around obstacles and go through openings. The wave is changed by passing through a hole or around an edge.

34. Section 12.3 Natural Frequency and Resonance page 203 Terms for Content Exam: • Node • Standing • Anti-node • Natural frequency • Destructive interference

35. Section 12.3 Natural Frequency and Resonance page 203 Natural frequency What is natural frequency? The natural frequency is the frequency at which a system oscillates when it is disturbed. The pendulum also had a natural frequency.

36. Section 12.3 Natural Frequency and Resonance page 203 Natural frequency Why natural frequency is important. The student needs to read the four reasons of natural frequency.

37. Section 12.3 Natural Frequency and Resonance page 203 Natural frequency Changing the natural frequency The natural frequency depends on many factors, such as the tightness, length, or weight of the string. Factors that affect natural frequency include size, inertia, or forces on the system.

38. Section 12.3 Natural Frequency and Resonance page 204 Resonance

39. Section 12.3 Natural Frequency and Resonance page 205 Standing waves on a string

40. Section 12.3 Natural Frequency and Resonance page 206 Interference Interference defined Constructive interference Destructive interference

41. TBW Chapter 12: Wavespages 207-209 Vocabulary Review – page 207 Write questions and answers for all sets. Concept Review – page 208 Write all questions and answers. Problems – page 209 Write all questions and answers.