6 2 Wave Phenomena Wave Interference As the

6. 2 Wave Phenomena

Wave Interference As the waves move outward from their respective sources, they pass through one another.

Wave Interference As they pass through one another, the waves interact to form an interference pattern of light and dark bands.

Constructive Interference When two waves arrives simultaneously at the same place IN PHASE = a crest from A arrives and they are IN phase… simultaneously with a crest from B 1. The amplitudes of the waves are ADDITIVE 2. The resultant waves has twice the amplitude of the individual waves from A and B

Destructive Interference When two waves arrives simultaneously at the same place OUT PHASE = a crest from A and they are OUT of. OF phase… arrives simultaneously with a trough from B 1. The two waves CANCEL each other

Wave Interference Occurs with all sorts of waves and you can see, hear the effect of this in everyday life

Observing Interference 1. Hold one end of the spring, and have a partner hold the opposite end. 2. One of you will generate a transverse pulse, and observe its motion along the spring. 3. After the pulse has dissipated, the other member of the team will generate an identical pulse. What will happen when you and your partner generate pulses simultaneously? Try it!! What did you observe? Did you see the expected result?

Observing Interference 1. Repeat the previous procedure, BUT now create two waves with the opposite displacements What will happen when you and your partner generate opposite pulses simultaneously? Try it!! What did you observe? Did you get the expected result?

Thomas Young’s Double Slit Experiment ØShowed that light is a wave!!

Thomas Young’s Double Slit Experiment Øhttp: //www. youtube. com/watch? v=Iuv 6 h. Y 6 zsd 0 Øhttp: //www. youtube. com/watch? v=M 4_0 ob. Iw. Q_U

Thomas Young’s Double Slit Experiment ØCreated a series of bright (constructive interference) and dark (destructive interference) bands ØAt C, D, and E, the crests arrived simultaneously and troughs arrived simultaneously ØAt dark bands (called NODAL LINES), LINES the crests and troughs arrived at the same time = cancel each other = no light

The experiment allows calculating WAVELENGHT ØThe difference between AC and BC is BF = ØUsing trigonometry you can find out that λ

Diffraction ØWhen a wave spreads out as it passes through a narrow opening, around corners or small obstacles

ØIf you stand on the street while an ambulance speeds by with its siren on, you will notice the pitch of the siren change. ØThe pitch will be higher as the ambulance approaches and will be lower as it moves away. How can we account for this change in pitch?

The Doppler Effect = The Frequency Shift ØThis was explained by a guy named C. J. Doppler

The Doppler Effect = The Frequency ØIf an ambulance is parked, Shift an observer and a driver of the ambulance hear the same pitch (frequency)

The Doppler Effect = The Frequency If an ambulance is moving, Shift the wave fronts reach an observer in front of the ambulance (Observer A) more often than they would if the ambulance were stationary = frequency heard by Observer A is greater than the source frequency

The Doppler Effect = The Frequency If an ambulance is moving, Shift the wave fronts reach an observer behind the ambulance (Observer C) less often than they would if the ambulance were stationary = the frequency heard by Observer C is less than the source frequency

The Sound Barrier, Shock waves and Sonic Boom Read on your own, it will not be on a test

6. 2 Review Questions (all except 7, 9, 10)

Chapter 6 Review Questions (all except 14, 15)