Chapter 11: WAVES

1. Chapter 11: WAVES Section 1-The Nature of Waves

3. Examples of waves… • A surfer waits for the perfect wave • Microwaves warm up leftover pizza • A CD player brings music (sound waves) to your ears More examples of waves… • Earthquakes--Energy is transferred in powerful waves that travel through Earth. (Seismic waves) • Light--A type of wave that can travel through empty space to transfer energy from the Sun to the Earth.

4. Drop a rock into a pool of water • The rock has ENERGY • ENERGY is transferred to nearby water molecules • These molecules transfer ENERGY to other molecules • A wave is a repeating disturbance or movement that transfers ENERGY through matter or space.

5. MECHANICAL WAVES • Waves that can travel only through matter are called mechanical waves. (Ex. Sound waves require air.) • The matter the waves travel through is called the medium. • The medium can be a solid, a liquid, a gas or a combination of these. Examples of mediums… • Sound waves = AIR • Ocean waves = WATER • Not all waves need a medium. Light and radio waves travel through space.

6. There are 2 types of mechanical waves: 1— TRANSVERSE • Matter in the medium moves back and forth at right angles to the direction that the wave travels. Examples—ocean wave, rope

7. 2—COMPRESSIONAL • Matter in the medium moves back and forth in the same direction that the wave travels. • Examples—slinky, sound waves

8. SEISMIC WAVES • During an earthquake, Earth’s crust vibrates, creating seismic waves that carry ENERGY outward. • These waves are a combination of TRANSVERSE and COMPRESSIONAL waves. • Compressional—P-wave • Transverse—S-wave

9. Chapter 11: WAVES Section 2-Wave Properties

10. What makes waves different from each other? • The mediumthey travel in • How much energy they carry • How fast they travel • What they look like • What do they look like? TRANSVERSE WAVES— Have alternating high points (crests) and low points (troughs).

12. Compressional waves do not have crests or troughs. • Compressional waves are made of 2 regions: 1. COMPRESSION-coils are close together (dense) 2.RAREFACTION-coils are far apart (less dense)

16. A wavelength is the distance between a point on a wave and the nearest point just like it.

17. FREQUENCY The frequency of a wave is the number of wavelengths that pass a fixed point each second.

18. Frequency = f

19. THE ELECTROMAGNETIC SPECTRUM

20. Frequency • Frequency is expressed in hertz (Hz). • A frequency of 1 Hz means that 1 wavelength passes by in 1 second. • In SI units, 1 Hz is the same as 1λ/s. • This relationship is always true— as frequency increases, wavelength decreases. f↑ = λ↓

21. WAVE SPEED • SPEED = WAVELENGTH X FREQUENCY • v=λx f • (λ=2m, f=3Hz) • v = 2m x 3Hz (3λ/s) • v = 6m/s

22. Wave Speed • SPEED = WAVELENGTH X FREQUENCY • v=λx f Example: (do on your own)λ= 3 m, f = 10 Hz

23. Why do some earthquakes cause terrible damage, while others are hardly felt? • Because the amount of energy a wave carries can vary. • AMPLITUDE is related to the ENERGYcarried by a wave. • ↑wave’s AMPLITUDE = ↑ wave’s ENERGY

25. If you’ve ever been knocked over by an ocean wave, you know that the higher the wave, the more energy it carries.

26. CHAPTER 11: WAVES Section 3-The Behavior of Waves

28. DIFFUSE REFLECTION—ROUGH SURFACES REFLECTION-LIGHT WAVES THE LAW OF REFLECTION—REGULAR/SMOOTH SURFACES

29. REFLECTION—REGULAR OR DIFFUSE?

30. REFLECTION—ALBEDO VALUES

31. REFLECTION—SOUND WAVES

32. When the sound waves strike an object, the waves are reflected back the to the bat. REFLECTION—Echolocation—(bats and dolphins) Bat emits sound waves as they fly.

33. REFLECTION If you are one of the last people to leave the school building…when you close your locker door, the sound echoes down the empty hall. ECHOES are caused by wave reflection. REFLECTION occurs when a wave strikes an object and bounces off of it. (Examples--sound, light, water) ECHO (REFLECTION OF SOUND WAVES)--Sometimes when the sound waves hit another object, they reflect off of it and come back to you. Your ears hear the sound again, a few seconds after you first heard your locker door slam.

34. SONAR—uses sound waves to find objects that are underwater.

35. These sound waves form images of her fetus. ULTRASOUND—ultrasonic waves are directed into a pregnant women’s uterus to form images of her fetus. Ultrasonic waves are directed into a pregnant woman’s uterus.

36. CAFETERIA AND STAGE

37. GYM AND CHORUS ROOM

38. REFRACTION Remember that a wave’s speed depends on the medium it is moving through. When a wave passes from 1 medium to another—such as when a light wave passes from air to water—it changes speed. REFRACTION is the bending of a wave caused by a change in its speed as it moves through 1 medium to another. (Example—RAINBOWS—LIGHT WAVES PASS FROM AIR TO WATER)

39. REFRACTION

41. The pencil looks like it is broken at the surface of the water. REFRACTION To the observer on the side of the pool, the swimmer’s feet look closer to the surface than it actually is.

42. DIFFRACTION • DIFFRACTION occurs when an object causes a wave to change direction and bend around it. • DIFFRACTION and REFRACTION both cause waves to bend. • The difference is that refraction occurs when waves pass through an object, while diffraction occurs when waves pass around an object. • ALSO--refraction changes mediums diffraction stays in the same medium

43. DIFFRACTION

44. INTERFERENCE When 2 or more waves OVERLAP and combine to form a new wave, the process is called INTERFERENCE.

45. DESTRUCTIVE--SUBTRACT INTERFERENCE CONSTRUCTIVE--ADD

46. INTERFERENCE