Section 1 The Nature of Waves

1. Section 1 The Nature of Waves

2. Wave • any disturbance or movement that transmits energy through matter or space • Waves carry energy without transporting matter.

3. All waves are produced by something that vibrates. • Medium—a material through which a wave travels. • solid, liquid, or gas • Not all waves need a medium Ex: Electromagnetic waves

4. Types of Waves • 3 kinds: • Transverse • Longitudinal • Surface

5. Transverse waves—waves in which the particles vibrate with an up-and-down motion. animation

6. Longitudinal waves—the particles in the medium vibrate back and forth along the path that the wave travels. animation

7. Surface waves- when a transverse and longitudinal wave combine. • Example: ocean waves

8. Section 2: Properties of Waves

9. Ways waves differ • How much energy they carry • How fast they travel • How they look

10. n • Wavelength—the distance between any two adjacent crests or compressions in a series of waves.

11. Transverse waves have crests—the highest points, and troughs—the lowest points.

12. Longitudinal waves have dense regions called compressions and less dense regions called rarefactions.

13. Wavelength • Distance between one point on a wave and the nearest point just like it • Ex. crest to crest or trough to trough, compression to compression, rarefaction to rarefaction

14. Amplitude—the maximum distance the wave vibrates from its rest position. • The more energy a wave carries, the greater its amplitude.

15. Amplitude of longitudinal waves • denser compressions = larger amplitude = more energy the wave carries • less dense rarefactions = larger amplitude = more energy the wave carries A B

16. Amplitude of transverse waves • The distance from the crest or trough of a wave to the normal position of the medium

17. Frequency—the number of waves produced in a given amount of time.Expressed in hertz (Hz)

18. Higher frequency means more energy. As frequency increases, wavelength decreases.

19. Wave Speed • Wave speed is the speed at which a wave travels. • Wave speed (velocity) = wavelength x frequency

20. Light waves travel faster than sound waves. • Sound waves travel faster in liquids and solids than in gas. • Light waves travel faster in gases and empty space than in liquids and solids.

21. DISCUSSION QUESTION: • In a thunderstorm, why do you see the lightning before you hear the thunder? • Light waves travel much faster than sound waves.

22. Section 3: Wave Interactions • Reflection occurs when a wave strikes an object and bounces off of it. • All types of waves can be reflected.

23. Refraction—the bending of a wave caused by a change in its speed as it moves from one medium to another • greater change in speed = more the wave bends.

24. wave passes into a material that slows it down, it is bent toward the normal • wave passes into a material that speeds it up, it is bent away from the normal.

25. Diffraction—an object causes a wave to change direction and bend around it

26. If obstacle < wavelength, wave diffracts a lot. • If obstacle > than the wavelength, wave does not diffract much. • The larger the obstacle is compared to the wavelength, the less the waves will diffract.

27. Interference— two or more waves combine, form a new wave • Waves pass through each other, continue in their original direction • New wave exists only while the original waves continue to overlap.

28. Constructive interference—waves add together

29. Constructive Interference

30. Destructive interference—waves subtract from each other • D.I.

31. Destructive Interference

32. Standing waves—a wave pattern that stays in one place • Form when waves of = wavelength and amplitude traveling in opposite directions continuously interfere with each other. • Nodes—the places where two waves always cancel each other

33. Resonance—the ability of an object to vibrate by absorbing energy at its natural frequency