1. Some examples of mechanical waves are: water waves, sound waves,
and the waves that travel
along a spring.
2. To move, mechanical waves require a transmitting medium.
3. Examples of electromagnetic waves are: TV, radio, light, and X rays.
4. Although electromagnetic waves can travel through a vacuum, they
can also travel through a
transmitting medium.
5. All electromagnetic waves travel at the same speed, 3 * 10 8 m/s.
6. Mechanical waves that are visible, e.g., water waves, are used to
study invisible electromagnetic
waves because the general properties of both types
of waves are the similar.
7. A third general type of wave is the matter wave, shown under certain conditions by electrons.
8. The two general divisions of mechanical waves are: transverse and longitudinal.
9. Stretch a spring between two people and then have one of them shake
their end up and down
to make transverse waves in it. Squish together
and then release some coils to start a longitudinal
wave travelling along a spring.
10. Piano and guitar strings transmit transverse waves. Fluids, liquids,
gases and plasmas usually
transmit only longitudinal waves.
11. Floating particles are moved in an oval or circular fashion by waves passing underneath them.
12. Energy moving through deep ocean water travels in longitudinal waves.
13. Some people mistakenly think that waves push floating objects ahead of them.
14. Water at the ocean's surface, just like the particles floating there, moves in a circular or oval fashion.
15. a) A third general type of mechanical wave is the surface wave.
b) A surface wave is the combination
of transverse and longitudinal waves, hence the oval motion
of surface water.
16. A wave pulse is a single crest or trough moving through a medium.
A regular sequence of them is a
wave train or a travelling wave. If
the energy source vibrates with simple harmonic motion, it will
send a continuous travelling wave moving
through the medium.
17. Student diagram.
18. Many waves can pass through one spot at the same time.
19. Only the properties of the transmitting medium determine the speed of waves passing through it.
20. The temperature of air, the depth of water and the density of a
spring control the speed of waves
passing through them.
21. A wave's amplitude indicates the amount of energy it transfers.
22. If a large amplitude wave and a small amplitude wave are moving
through the same medium, they
will travel at the same speed.
23. Recall that only the properties of a medium determine the speed of waves travelling through it.
24. Frequency and wavelength are inversely related. A high frequency
wave will have a short
wavelength while a low frequency wave
will have a long wavelength.
25. Student diagrams.
26. See Figure 14-8, p 294.
27. When a wave contacts a boundary, the frequencies of the incident
and transmitted waves are the
same. 28. The figure
shows that, although the transmitted wave is shorter, it moves more slowly
than the longer but faster moving incident
wave. As a result, the frequencies of the incident and
transmitted waves do match.
29. As noted in Q. 28, the speeds of the incident and transmitted waves are different.
30. The unequal speeds occur because the media in which the two waves
travel have different
properties.
31. If the two media are similar:
a) the behavior of the incident and
transmitted waves is similar.
b) the amplitude of the transmitted
wave will be only slightly less than that of the incident wave.
c) the amplitude of the reflected wave
will be much less than that of the incident wave because not
much energy
reflects back.
d) the incident and transmitted waves
will have similar speeds because the properties of the two
media are similar.
e) the energy of the incident and transmitted
waves will be similar.
32. If the two media are similar, most of the incident wave's energy will move into the new medium.
33. a) A crest returns from a boundary with a more dense material as
a crest.
b) Not much energy moves into the new
medium.
c) As a result, most of the incident
wave reflects.
34. Student diagram. Refer to Figure 14-10, p 295.
35. A crest returns from a boundary with a less dense material as a trough.
36. Student diagram. Refer to Figure 14-9, p 295.
37. Superposition causes waves of unexpectedly large or small height.
38. There is constructive and destructive interference.
39. When waves meet in phase, wave height increases.
40. When waves meet out of phase, wave height decreases.
41. Energy pulses pass through each other unaffected.
42. Two nodes, points of no vibration, occur on either side of an antinode,
a zone of maximum
vibration.
43. In a standing wave, the locations of the nodes and antinodes are constant.
44. A ray is an arrow showing the path energy takes through a medium.
It is drawn at 900 to the
crests of waves moving through the medium.
45. As we use the term here, rays are only visual aids and do not exist.
46. Waves can show rectilinear propagation, reflection, refraction and
diffraction. Diffraction from
adjacent apertures results in an interference
pattern. See Figures 14-20a and b, p 301.
47. Student diagrams.
48. Waves of small wavelength generate minimal diffraction. Or, as the
size of the aperture increases,
the degree of diffraction decreases.