Characteristics of Waves

1. Characteristics of Waves Chapter 15, pages 472-492

2. Weekly Target • We are learning to demonstrate how waves transfer energy. • We are looking for a disturbance or variation that transfers energy from on point to another point in a medium. • Transverse waves – wave and medium move in direction that is perpendicular to each other. • Longitudinal waves – wave and medium move in same direction.

3. What are Waves? • A wave is a disturbance that transfers energy from place to place • Waves travel through a material called a medium. • Waves that require a medium to travel through are called mechanical waves.

4. What are Waves? • Waves are created when a source of energy causes a medium to vibrate. • A vibration is a repeated back-and-forth or up-and –down motion.

5. Classification of Waves • Wave are classified according to how they move. • Types of waves: 1. Transverse 2. Longitudinal 3. Surface

6. Transverse Wave • In transverse waves, the particles of the medium move perpendicular in the direction of the wave. • Parts of the transverse wave: • Crest • Trough • Wavelength • Amplitude

7. Longitudinal Wave • In longitudinal waves, the particles of the wave move parallel to direction of the wave movement. • Parts of the wave: • Compressions • Rarefactions • Wavelength

8. Surface Wave • Surface waves occur at the boundary between two mediums and are a combination of transverse and longitudinal waves.

9. A transverse wave….. 10 • Vibrates particles perpendicular to the direction of wave • Vibrates particles parallel to the direction of the wave • Vibrates both parallel and perpendicular to the direction of the wave • Vibrates particles in one direction • Help! I don’t understand.

10. What type of wave is represented by picture? • Transverse • Longitudinal • Surface • Seismic • Help! I don’t understand. 10

11. A wave is a disturbance that transfers • matter. • particles. • energy. • a medium. • Help! I don’t understand. 10

12. What do you call the material that a wave travels through? • Plasma • Space • Vacuum • Medium • Help! I don’t understand. 10

13. What type of wave is represented by the animation? 10 Seconds Remaining • Longitudinal • Transverse • Surface • Seismic • Help! I don’t understand.

14. Transverse Wave

15. Longitudinal Wave

16. We are learning to: describe the properties of waves.We are looking for: Wavelength-distance from crest to crestFrequency-number of waves that pass a given point each secondAmplitude-distance from rest position to the crest

17. Properties of Waves • The basic properties of waves are amplitude, wavelength, frequency, and speed.

18. Amplitude • Amplitude is the maximum distance the particles of the medium carrying the wave move away from their rest position. • Measured from crest to resting position.

19. Wavelength • Wavelength is the distance between corresponding parts of a wave. • Wavelength is measured from crest to crest.

20. Frequency • Frequency of a wave is the number of complete waves that pass a given point in a certain amount of time. • Frequency is measured in hertz.

21. Wave Speed • Wave speed is how far the wave travels in one unit of time, or distance divided by time.

22. Mathematical Relationship • The speed, wavelength, and frequency of a wave are related to each other by a mathematical formula: Speed=wavelength x frequency

23. In the diagram, identify the wave property “A” 10 • Frequency • Amplitude • Wavelength • Help! I don’t understand.

24. Which of the following is true about waves in the diagram? • Wave X has a higher frequency than Wave Y • Wave X has a lower frequency than Wave Y • Wave X has the same frequency as Wave Y • Help! I don’t understand. :10

25. Which of the waves in the picture has the greatest amplitude? 1 2 • 1 • 2 • 3 • Help! I don’t understand. 3 10

26. Which property measures the amount of energy transferred by a wave? • Wavelength • Frequency • Amplitude • Help! I don’t understand. 10

27. We are learning to demonstrate how waves transfer energy. We are looking for how waves interact with an object or other waves.  They either: Transmit-wave energy passes through an object. Reflect-wave energy bounces off an object. Absorb-wave energy is taken in by an object they encounter. Interference-wave energy of multiple waves is combined.

28. Interaction of Waves • When waves interact, three things can happen to the waves: • Reflect • Refract • Diffract

29. Reflection • Reflection happens when waves bounce off of a barrier. • The angle of incidence is the angle between the incoming wave and the imaginary perpendicular line. • The angle of reflection is the angle between the reflected wave and the imaginary perpendicular line.

30. Law of Reflection • The angle of reflection is equal to the angle of incidence.

31. Refraction • Refraction occurs as the wave go between different mediums. • The speed of a wave changes as the medium changes. • The change in speed of the wave causes the waves to bend.

32. Diffraction • Diffraction is the bending of waves as the waves go through a small opening or around a corner. • As the wave goes through the hole or around the corner, it spreads out and bends.

33. What is it called when a wave bounces off of a barrier? • Diffraction • Reflection • Refraction • Help, I don’t understand. 10

34. What happens to waves as they go through an opening or around a corner of an object? • They are diffracted. • They are reflected. • They are refracted. • Help, I don’t understand. 10

35. As waves go through different mediums, what happens to them? • Waves change speed and are diffracted. • Waves change speed and are reflected. • Waves change speed and are refracted. • Help, I don’t understand. 10

36. Interference • Interference occurs as two or more waves interact. • Constructive interference happens when waves meet and the amplitude increases. • Destructive interference happens when waves meet and the amplitude decreases.

37. Standing Waves • Standing waves form as the original wave is interfered with by the reflected wave. • The standing wave has a node and an antinode.

39. What happens to the energy of the wave when the crest of the blue wave meets the crest of the green wave? • Energy decreases. • Energy increases. • Energy stays the same. • I don’t get it! Help! 10

41. Review Questions • What do we call the transfer of energy from place to place? • (wave) • What do we call the material through which waves travel? • (medium) • When the medium _______________, a wave is created. • (vibrate) • How are waves classified? • (how they move)

42. Review Questions • The highest part of a transverse wave is called the _______________. • (crest) • The lowest part of a transverse wave is called the _______________. • (trough) • What type of wave travels parallel to the direction of the wave travel? • (longitudinal) • What type of wave travels perpendicular to the direction of the wave travel? • (transverse)

43. Review Questions • What type of waves is on top of a pond or lake? • (surface) • What property of a wave is the maximum distance that particles of the medium move from resting position? • (amplitude) • What do we call the distance between two corresponding parts of a wave? • (wavelength) • In what units is frequency measured? • (hertz)

44. Review Questions • What is the mathematical relationship between speed of a wave, frequency and wavelength? • (speed = wavelength x frequency) • When a wave hits a barrier and bounces back, it is called _______________. • (reflection) • When a wave bends because it changes speed as it travels through different mediums, it is called _______________. • (refraction) • When a wave bends as it travels around the edge of a barrier it is called _______________. • (diffraction)

45. Review Questions • The interaction between two waves is called ________________. • (interference) • Waves combine to make a wave of larger amplitude is called ______________. • (constructive interference) • Waves combine to make a wave of lower or no amplitude is called _______________. • (destructive interference) • What type of wave are two waves that interfere with each other as they pass each other? • (standing)

46. Review Questions • What occurs when the vibration matches the natural frequency of the object? • (resonance) • What are the highest and lowest points called on a standing wave? • (antinodes) • What are the points of zero amplitude called on a standing wave? • (nodes) • What type of waves does an earthquake produce? • (seismic)

47. Review Questions • Longitudinal seismic waves are called _______________. • (primary) • Transverse seismic waves are called _______________. • (secondary) • Which type of seismic wave causes the most damage? • (surface) • Which seismic wave is the fastest? • (primary)

48. Review Questions • What type of waves requires a medium to pass through? • (mechanical) • What name is given to the waves produce by underwater earthquakes? • (tsunamis) • What machine measures ground movement? • (seismograph) • What scale is used to measure the magnitude of seismic waves? • (Richter)

49. Review Questions • What are the areas of a longitudinal wave where the waves are close together? • (compressions) • What are the areas of a longitudinal wave where the waves are far apart? • (rarefactions) • What is the angle defined by an incoming wave and the imaginary perpendicular line? • (angle of incidence) • What is the angle defined by a reflected wave and the imaginary perpendicular line? • (angle of reflection)

50. Review Questions • What is the relationship between the angle of incidence and the angle of reflection? • (they are equal to each other)