1. Today 1/16  Waves  Interference of Waves  HW:1/16 HW Handout “Superposition” Due Wed, 1/22 (beginning of class)  Read: Ch 16.1,2,5 Ch 17.1,2  Suggest: Problems 16-1,2,3,4,5,8  Note: This “lecture” is mostly animations and is more than 80 slides long! Beware the print button!

2. Things to think about: How would you define a “wavelength?” How would you define a “frequency?” How would you define a “wave velocity?” What happens when two waves run into each other? Consider a traveling wave: sound, light, football stadium, water... How does the direction of the wave’s motion compare to the direction of the individual particle’s motion?

12. Wave moves right while particles move up and down. Called a “transverse wave” Examples are light, water, and football stadium, sound is a “longitudinal wave.”

38. Wavelength ( ) = ? = 8 units Wave Velocity (v) = ? Direction is to the right, v =  x/  t v = /T  x is and  t is T, the time for a particle to go through one complete oscillation, as in SHM. Frequency, f = 1/T also as in SHM. v = f

39. What happens when two waves collide?

43. waves just meeting

44. ? Superposition!!! Green wave says move up but blue wave says move down so... Particle does not move!! ?? Superposition means “superimpose” all effects at a chosen location then add them up (as vectors) to get the “net” effect at that location.

47. Only overlap here. the two waves are right on top of one another.

57. Now let’s put this in motion.

58. Destructive interferenceConstructive interference

59. Destructive interferenceConstructive interference

60. Destructive interferenceConstructive interference

61. Destructive interferenceConstructive interference

62. Destructive interferenceConstructive interference

63. Destructive interferenceConstructive interference

64. Destructive interferenceConstructive interference

65. Destructive interferenceConstructive interference

66. Destructive interferenceConstructive interference

67. Destructive interferenceConstructive interference

68. Destructive interferenceConstructive interference

69. Destructive interferenceConstructive interference

70. Destructive interferenceConstructive interference

71. Destructive interferenceConstructive interference

72. Destructive interferenceConstructive interference

73. Destructive interferenceConstructive interference

74. Destructive interferenceConstructive interference

75. Destructive interferenceConstructive interference

76. Destructive interferenceConstructive interference

77. Destructive interferenceConstructive interference

78. Destructive interferenceConstructive interference

79. Destructive interferenceConstructive interference

80. Destructive interferenceConstructive interference This is a “standing wave” and is a “superposition” of two traveling waves. These two waves “interfere” with each other causing locations of “constructive” and “destructive “ interference.

81. Destructive interferenceConstructive interference Note that the locations of “constructive” and “destructive “ interference alternate. These locations are called “nodes” (destructive) and “anti-nodes” (constructive).

82. Your first Homework...