Waves

1. Waves

2. The Nature of a Wave • A wave is a rhythmic disturbance that carries energy through matter and space. • A wave pulse is a single disturbance that travels through a medium. • A continuous traveling wave is a repeating and periodic disturbance which moves through a medium.

3. 10 The source of all wave motion is a • movement of matter • harmonic object • vibration • amplitude

4. 10 Waves are the transfer of • energy • matter • vibrations • water

5. What is a medium? • A medium is a substance or material which carries the wave. • The wave medium is not the wave and doesn’t make the wave; it merely carries or transports the wave from its source to another location.

6. 0 A trumpet player is in the band room practicing his music for the half-time show. What is the medium which carries the sound wave? • The trumpet • The music he is producing • The air in the room • There is no medium

7. Types of Waves • Mechanical waves • Electromagnetic waves • Matter wave

8. Mechanical waves • Mechanical waves require a material medium • Newton’s laws govern the motion of mechanical waves • The speed of mechanical waves depends on the temperature of the medium • Examples of mechanical waves include: water waves, sound waves, and waves that travel along a rope or spring

9. Electromagnetic waves • No medium is needed for the motion of electromagnetic waves • All electromagnetic waves travel at a speed of 2.9979 x 108 m/s in a vacuum. • The details of electromagnetic waves cannot be observed directly • Examples of electromagnetic waves include: light waves, radio waves, microwaves, and X-rays

10. Electromagnetic Spectrum

11. Which of the following electromagnetic waves travel the fastest at room temp? 10 • Radio • Microwave • X-rays • None of the above

12. Which of the following is NOT an electromagnetic wave? 10 • Radio • Sound • Light • X-fays

13. Matter waves • Electrons and other particles show wave-like behavior under certain conditions. • Quantum mechanics is needed to describe the properties of matter waves.

14. 10 The type of wave that does not require a medium is a(n) • electromagnetic wave • mechanical wave • matter wave • All waves require a medium

15. 10 The type of wave that travels at 3.0 x 108 m/s is a(n) • electromagnetic wave • mechanical wave • matter wave • All waves travel at this speed

16. 10 This type of wave is governed by Newton’s laws of motion. • Electromagnetic wave • Mechanical wave • Matter wave • All types of waves

17. 10 The properties of this type of wave are described by quantum mechanics. • Electromagnetic waves • Mechanical waves • Matter waves • All types of waves.

18. 10 Sound is an example of this type of wave. • Electromagnetic • Mechanical • Matter • All of the above

19. 10 Light is an example of this type of wave. • Electromagnetic • Mechanical • Matter • All of the above

20. Types of Mechanical Waves • Transverse waves • Longitudinal or compressional waves • Surface waves

21. Transverse waves • A transverse wave causes the particles of the medium to vibrate perpendicularly to the direction of the motion of the wave. • The highest point of a transverse wave is called a crest. • The lowest point of a transverse wave is called a trough. • Examples of transverse waves include: waves in piano and guitar strings

22. Transverse Waves

23. Longitudinal waves • A longitudinal wave causes the particles of a medium to move parallel to the direction of the motion of the wave. • The point in which the medium is compressed (pressure is increased) is called the compression. • The point in which the pressure in a medium is lowered is called the rarefaction. • Examples of longitudinal waves include: sound waves

24. Longitudinal Waves

25. Surface waves • Surface waves are a mixture of transverse and longitudinal waves • The particles in the medium move both parallel and perpendicular to the direction of the wave • Examples of surface waves include: water at the surface of the ocean

26. Surface Waves

27. 10 A sound wave is an example of a ___ wave. • longitudinal • transverse • standing • constructive

28. 10 A mechanical wave in which the vibration of the individual particles are perpendicular to the direction of the wave is called a ___ wave. • longitudinal • sound • transverse • compression

29. Measuring a Wave • Wavelength (λ)- The shortest distance between points where the wave pattern repeats itself. (Measured in units of length). • Frequency (f)- The number of complete vibrations per second measured at a fixed location. (Measured in hertz-Hz) • Period (T)-The shortest time interval in which the motion repeats itself (Measured in seconds) • Amplitude- The maximum displacement from the rest or equilibrium position. A wave with a larger amplitude transfers more energy.

30. Measuring a Wave

31. Relationships between wave properties • Wavelength and frequency are inversely related. As wavelength increases, frequency decreases. • Frequency and period are inversely related. (f=1/T or T=1/f) • The velocity of a wave is equal to the distance it can travel in a given time period. v=d/t or v=λ/T or v=λf

32. 10 The time needed for a wave to make one complete cycle is its • frequency • period • wavelength • amplitude

33. 10 The amplitude of a wave is 1 meter. The top-to –bottom distance of the disturbance is • 0.5 m • 1 m • 2 m • None of the above

34. 10 If you double the frequency of a vibrating object, its period • doubles • halves • is quartered

35. 10 During a single period, the distance traveled by a wave is • one-half wavelength • one wavelength • two wavelengths

36. Wave Behavior • The speed of a wave depends only on the properties of the medium it passes through, not on the wave’s amplitude. • For example: the speed of the slinky did not change when you increased the amplitude-only when you increased the length. • As the tension of the spring increases, the speed of the wave increases.

37. Waves at Boundaries • The wave that strikes a boundary is called the incident wave. • The wave that returns after striking a boundary is called the reflected wave. • If the boundary is fixed (like a rigid wall), the reflected wave has the same amplitude as the incident wave but is inverted (downward). • http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave6.html • If the boundary is flexible (like a spring), the reflected wave is upward (erect) and is only partially reflected (amplitude is smaller). Part of the wave is also transmitted. • http://paws.kettering.edu/~drussell/Demos/reflect/reflect.html

38. 10 When a wave encounters a boundary, the wave that strikes the boundary is called the • incident wave • reflected wave • refracted wave • normal wave

39. 10 When a wave encounters a boundary, the wave that returns is called the • incident wave • reflected wave • refracted wave • normal wave

40. 10 When a wave is sent down a spring connected to a wall, ___of the energy in the wave is reflected back. • all • none • some

41. 10 A pulse is sent along a spring that is attached to the wall. The reflected pulse is • inverted with equal amplitude • inverted with a smaller amplitude • upright with equal amplitude • upright with a smaller amplitude

42. Superposition of Waves • When two waves exist in the same place in the medium at the same time, each wave affects the medium independently. • The displacement of a medium caused by two or more waves is the algebraic sum of the displacements caused by the individual waves. This is called the Principle of Superposition.

43. Interference • The result of superposition is called interference. • Destructive interference occurs when waves have equal but opposite amplitudes. • When the pulses meet and are in the same location, the displacement is zero. • This point (which doesn’t move at all) is called the node. • The waves pass through each other unchanged. • http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave3.html

44. Interference (continued) • Constructive interference occurs when the wave displacements are in the same direction. • The result is an amplitude that is greater than any of the individual waves. • A large pulse appears at the point where the two waves meet. • This point has the largest displacement and is called the antinode. • The waves pass through each other without changing their shapes or sizes. • http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave2.html • http://www.sciencejoywagon.com/explrsci/media/interfer.htm

45. 10 ___ occurs when two or more waves move through a medium at the same time. • Refraction • Reflection • Interference • Resonance

46. 10 In destructive interference, a point that experiences no displacement is called a • crest • trough • node • antinode

47. Standing Waves • A standing wave is a wave that appears to be standing still. • Standing waves result from the interference between the incident wave and the reflected wave. • As the frequency of the vibrations is increased, the number of nodes and antinodes increases. (see figure 14-14 on page 389) • http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave5.html • http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave4.html

48. Waves in Two Dimensions • Reflection occurs when a wave changes direction after striking a barrier. • Ray diagrams model the movement of waves. A ray is a line drawn at right angles to the crests of waves. • The incident ray is the ray pointing toward the barrier. • The reflected ray is the ray pointing away from the barrier. • The barrier is represented by a line. • The normal is a line drawn perpendicular to the barrier.

49. Ray Diagram of Wave Angle of reflection Normal Angle of incidence Angle of incidence Normal Angle of reflection

50. Law of Reflection • The law of reflection states that the angle of incidence is equal to the angle of reflection. • The angle of incidence is the angle between the normal and the incident ray. • The angle of reflection is the angle between the normal and the reflected ray.