1. Poster Homework As partners, make a poster that teaches all we have learned: wave, wave pulse, medium, continuous wave, speed of wave, period, frequency, the 2 equations.

2. Points for: 1) Include all terms (__/5) 2) Scientific accuracy (__/5) 3) More thorough than merely copying the lecture notes (use the book, etc. to learn more) (__/5) 4) Visual appeal & color (__/5) 5) Best in Class (__/5) Will be graded and voted on by your peers

3. Superposition Powerpoint/Guided notes

4. Amplitude Maximum distance from rest position

5. The principle of superposition: Particles cannot be at the same place at the same time. Waves can. When waves are at the same place at the same time, their energies add, meaning their amplitudes add.

9. The principle of superposition= When waves are at the same place at the same time, their energies add, meaning their amplitudes add. This phenomenon is also called interference.

10. Constructive interference When the wave pulse amplitudes are in the same direction (i.e., up) they add.

11. Destructive interference When the wave pulse amplitudes are in opposite directions (i.e. up and down), they subtract, lessening or even canceling each other out for a moment.

14. Standing Wave notes continued

15. Natural Frequency If I shake at just the right frequency, I will be pulling up during the crests, and down during the troughs. The oscillation will be much larger than the motion of your hand because of constructive interference.

16. Standing Waves, cont’d At the correct frequency, an object can be made to oscillate in a special way called mechanical resonance, or a standing wave. Adjust the period of your energy input so that it equals the time it takes for a wave to make one round-trip from your hand to the other end and back. Fairly instinctual, like pushing someone on a swing (at the right time and period)

17. Standing Waves cont’d The wave that results is called mechanical resonance, or a standing wave “Resonance” because of the large amplitude “Standing” because the wave appears to not be moving

18. Natural Frequency If I shake at just the right frequency, I will be pulling up during the crests, and down during the troughs. This produces maximum constructive interference = maximum amplitude Happens at that particular slinky/thing’s natural frequency.

19. Standing Wave The speed in a medium is constant, so shake at the frequency that will fit a wave perfectly on the string, and you have made a standing wave. Frequency depends on the medium (slinky), length (or shape) of the medium, and how many waves you want to fit on the medium. A whole number of half-wavelengths is fit on the slinky.

20. (the dots show onenode on eachstanding wave)

21. Nodes and Antinodes in a Standing Wave Places of maximum amplitude = antinodes Places of zero amplitude (no movement) = nodes A standing wave on a slinky appears to not be moving because there is no left-to- right movement of the nodes. There is one more node than antinode

22. Resonance The tendency of an object (slinky, etc.) to oscillate (vibrate) at a greater amplitude at some frequencies than at others. -Pushing someone on a swing -Singing to break glass -Sounds breaking kidney stones -Tacoma Narrows Bridge

23. To do the superposition worksheet and problem 45: First use a pencil to draw the triangles of the original traveling waves as they move along at a rate of one dot per unit time. When the waves are not touching, this is how the waves look When the waves overlap, you must add or subtract the amplitudes of the waves at each point. For instance an upwards amplitude of 2 added to a downwards amplitude of 1 equals an upwards amplitude of 1.

24. Superposition HW Try to demonstrate constructive interference and destructive interference on a slinky. Make harmonics 1, 2, 3, etc. as high as you can go on a slinky. Write and draw your strategy and waves for each. Read p. 338-340. Do worksheet, and do p 345 #18, 20, 45