1. K-12 Science, CCSD, 2006 9/11 p. 20 Waves Introduction Notes IQ: Put a check mark by things that you think involve wave action: Sun’s rays Musical instruments Earthquake Radios Water

2. K-12 Science, CCSD, 2006 Waves A wave is any disturbance that transmits/moves energy through matter or space through vibrations. A wave is energy, not matter being moved from one place to another.

3. K-12 Science, CCSD, 2006 Waves You can sometimes see a wave start. The energy moves out in all directions from the source.

4. K-12 Science, CCSD, 2006 The waves on the pond move toward the shore, but the water & the fishing lure floating on the surface don’t move w/the wave

5. K-12 Science, CCSD, 2006 Waves We draw waves to represent energy. If you vibrate a string, you demonstrate a wave. A vibration is a back and forth movement of an object. videovideo

6. K-12 Science, CCSD, 2006 The material a wave travels through is called a medium. Ex. Water (liquid) Air (gas) Ground (Solid)

7. K-12 Science, CCSD, 2006 Waves that NEED a medium to travel are called Mechanical waves. Ex. Sound, ocean waves. Waves that can travel without a medium are Electromagnetic waves. Ex. light, x- rays, microwaves.

8. EM Waves Require no medium to travel Can go through space Light/EM waves How do we know EM/light waves can go through space? (answer on pg ) Mechanical Waves Require a medium to travel Sound, slinky seismic & H 2 O are all examples Knowing this, what’s wrong/incorrect w/most SciFi movies, such as Aliens?! (answer on pg )

9. K-12 Science, CCSD, 2006 Types of Waves 1.Transverse Waves: particles move with an up and down motion, perpendicular to the direction of the wave. Ex. light waves. Video This is drawn like this:

10. K-12 Science, CCSD, 2006 Parts of a Transverse Wave A = Crest: highest pt. of wave B = Trough lowest point of wave D = 1 full wave = 1 wavelength C = Amplitude: height of wave C A B D

11. K-12 Science, CCSD, 2006 Parts of a T Wave

12. K-12 Science, CCSD, 2006 Types of Waves 2. Longitudinal waves/compressional waves: Particles move back and forth, (parallel) in the same direction as the wave’s energy. Ex. sound waves.

13. K-12 Science, CCSD, 2006 Parts of a Longitudinal Wave Compression: particles are pushed close together. Rarefaction: particles are spread apart. Video Video

14. K-12 Science, CCSD, 2006 Water waves Water waves have transverse and longitudinal characteristics. Energy is transferred, but the particles stay essentially in the same place

15. K-12 Science, CCSD, 2006 OQ: True or false: Waves transfer energy from one place to another and not particles.

16. K-12 Science, CCSD, 2006 9/17 Wave Properties Notes IQ: Which wave has a larger amplitude? How can you tell?

17. K-12 Science, CCSD, 2006 Wave Properties Amplitude- The distance from the rest position to the top of a crest, or from the rest position to the bottom of a trough. Wavelength- The length of one whole crest and one whole trough= 1 full wave

18. K-12 Science, CCSD, 2006 Frequency- The number of full waves passing through a point in one second. SI Unit is hertz. Ex. 10 waves per second = 10 hertz What is the frequency if 100 waves pass through a point in 20s?

19. K-12 Science, CCSD, 2006 Period: The amount of time it takes one wave to pass through a point. Inversely related to f. T=1/f Unit sec.

21. K-12 Science, CCSD, 2006 Speed- The distance travelled by a wave in a given amount of time, depends ONLY upon the medium. Ex. 100 meters in one second = 100 m/s. Speed= dist./time What is the speed of a wave that travels 50 m in 5 secs?

23. K-12 Science, CCSD, 2006 Wave Speed The Wave Speedpeed ttravels –ie: distance a crest or compression goes in a certain amount of time Depends on the medium the wave’s traveling through –Due to density variations –> dense = faster sound slower light –< dense = faster light slower sound Calculating wave speed: Wave speed (v) Wavelength (Λ) Frequency (f) v = Λ X f Unit = meters/sec (m/s)

24. Wave speed (v) Wavelength (Λ) Frequency ( f )

25. K-12 Science, CCSD, 2006 Frequency Large wavelength = low frequency Medium wavelength = medium frequency Small wavelength = high frequency

26. K-12 Science, CCSD, 2006 Frequency Don’t confuse the frequency with the speed of a wave. Here’s an analogy:

27. K-12 Science, CCSD, 2006 Frequency If you were looking down on a freeway... And all of the vehicles were going exactly 60 miles per hour (the same speed)...

28. K-12 Science, CCSD, 2006 Frequency Small cars going 60 miles per hour

29. K-12 Science, CCSD, 2006 Frequency Bigger cars going 60 miles per hour

30. K-12 Science, CCSD, 2006 Frequency Really big vehicles going 60 miles per hour

31. K-12 Science, CCSD, 2006 Frequency Speed = 60 miles per hour Small cars = high frequency (6) Bus = low frequency (1)

32. K-12 Science, CCSD, 2006 Frequency Light speed = 186,000 miles per second Blue light waves = higher frequency Red light waves = lower frequency

33. K-12 Science, CCSD, 2006 OQ: True or false? A wave with less frequency can be travelling faster than a wave with higher frequency.

34. K-12 Science, CCSD, 2006 9/16 p.24Bill Nye Waves IQ: Which of the following is the best representation of what probably happens to a sound wave travelling through the same medium over time if no more energy is added?

35. K-12 Science, CCSD, 2006 OQ: What is the speed of a wave that travels 50m in 100s?

36. K-12 Science, CCSD, 2006 9/17Waves Mini labs What is the frequency of the following wave if it happened over 2s? Calculate the speed of the wave using v= 20 m

37. K-12 Science, CCSD, 2006 OQ: What was the source of energy for the waves you made today? What is the medium? a.The slinky b.The table c.Your hand d.The air

38. K-12 Science, CCSD, 2006 OQ: Which of the following could NOT be used as evidence to prove that the medium itself does not move during the transfer of energy through a wave? (more than one answer possible) A.As a wave travels down a rope, the particles of the rope don’t get transferred down. B.Longer waves travel farther from their source than shorter waves. C. A piece of string tied to a slinky would not leave its place if a wave is created in the slinky. D. The soil does not get carried from 1 place to another during an earthquake.