1. Today’s Topic: Transverse/Longitudinal Waves Learning Goal: SWBAT quantify the differences between transverse and longitudinal waves and identify their uses. A sound wave of 250 Hz travels in 31 °C air. What is the wavelength of this wave? Another sound wave of 5,265 Hz travels 31 °C in air. What is the wavelength of this wave? What do you notice about the wavelength as frequency increases?

2. Homework Due Wednesday, 6/3: Complete the Wave Speed Worksheet One Day Late: Pendulum Lab Simple Harmonic Motion Worksheet

3. Types of Waves With this big slinky and two volunteers, let’s go into the hallway to demonstrate two different types of waves. What is similar between these two waves? What is different between these two waves?

4. Wave Types What we just saw are an example of the two different types of waves that exist: Transverse Waves and Longitudinal Waves. Whenever the motion of the medium is at right angles to the direction in which a wave travels, the wave is a transverse wave. Wave direction Motion of Medium

5. Transverse Waves One of the types of waves we saw with the slinky was a Transverse Wave. Which wave was the transverse wave? How do you know? Here are some other examples of transverse waves.

6. Transverse Waves Guitar Strings (Slow Motion Video) Snare Drums and Cymbals (Video) All electromagnetic waves (light, infrared, UV, Gamma, etc.)electromagnetic

7. Longitudinal Waves Not all waves are transverse waves. As seen in the slinky, sometimes the particles of the medium travel in the same direction as the wave. When the particles oscillate parallel to or along the direction of the wave (rather than right angles to it) the wave is a longitudinal wave. Wave direction Motion of Medium

8. Longitudinal Waves Sound waves are longitudinal waves.

9. Longitudinal Waves This air cannon is another example.air cannon Shockwaves are also examples of longitudinal waves Shockwavesexamples

10. Conceptual Check Where can you find Transverse Waves in music? Where can you find Longitudinal Waves in music?

11. Conceptual Check What types of waves do you see at the beach or in a puddle? Are these transverse or longitudinal waves?

12. Let’s focus on one dot a time…

13. Conceptual Check They are technically BOTH longitudinal and transverse. These are called surface waves.

14. Has Longitudinal Properties: And Transverse Properties:

15. Add them together! (Up and down, and side-to-side motion)

16. More Examples A bunch of people are standing in line outside of GameStop to get their copy of Halo 5. A jerk in the back of the line pushes the kid in front of him, who pushes the kid in front of him, etc… What type of wave is this? pulse direction

17. More Examples A crowd at a Rutgers Football Game are pretty excited at how the game is going. To show their excitement, they begin to do “the wave”. What type of wave this?this

18. Interference Waves are different from other types of things we deal with on a day-to-day basis. For example, let’s say I want to take two Physics books and combine them into each other, so they both occupy the same space at the same time. Meaning…

19. Wave Interference I want both books to overlap each other: We can’t do this, can we? But what about waves? Can we overlap sound waves over each other? Yes! We all do it all the time!

20. Wave Interference Waves, unlike objects made of matter (rocks, tables, etc.) can exist at the same time in the same place. This is because waves are a disturbance in a medium – they are not made of matter.

21. Wave Interference Let’s see a visualization of waves residing in the same place at the same time.

22. Superposition What we are seeing with that demonstration is an example of superposition. Superposition: The combination of two overlapping waves.

23. Overlapping Waves If we look close enough at this picture, we can see certain areas where the waves seem to interfere with one another.

24. Overlapping Waves Keep in mind that these waves, and ripples, are moving towards each other.

25. Interference Pattern

26. Overlapping Waves These waves superimpose onto one another creating an interference pattern. An interference pattern is a regular arrangement of places where wave effects are increased, decreased, or neutralized. The net displacement (amplitudes) are added together resulting in different interference.

27. Interference Pattern

28. Types of Interference Let’s pump the brakes. Imagine we have two crests coming towards each other like so: What will happen when these waves interfere and superimpose onto each other?

29. Types of Interference The resulting wave (in green) is taller than the two original waves: The same can happen with two troughs come together:

30. Constructive Interference This is an example of constructive interference. In constructive interference, the crest of one wave overlaps with the crest of another and their individual effects add together. The result is a wave of increased amplitude.

31. Types of Interference What if we have the following situation: Predict what will happen in this case. This is destructive interference.

32. Destructive Interference In destructive interference, the crest of one wave overlaps with the trough of another and their individual effects are reduced. The high part of one wave simply fill in the low part of another. The result is a wave of a reduced amplitude.

33. Destructive Interference These “spokes” you see here in the ripple tank are locations of where there is destructive interference. Let’s highlight them.

34. Types of Interference What about in this situation? Predict what will happen in this case. This is complete destructive interference.

35. Complete Destructive Interference In complete destructive interference, the instant the two pulses overlap, they completely cancel each other; it is as if there is no disturbance at all.

36. This Should Make More Sense Now

37. Example If we superimpose these waves on top of one another, what type of wave will we get? A B

38. Example What about now? A B

39. Example And now? A B

40. Example And now? A B

41. Example And now? A B

42. Example And now? A B

43. Example And now? A B