1. Waves
Chapters 10 & 12

2. The Nature of Waves
Chapter 10 Sections 1 & 2

3. What is a wave?
Def: a repeating movement that transfers energy through matter
Types of waves:
Transverse: matter (up/down) moves at right angles with the wave (left/right)

4. Other Types
Compressional: matter moves in the same direction as wave

5. Parts of a Transverse Wave

6. Parts of a Compressional Wave

7. Wave Properties
Wavelength: distance between one point on a wave an the next just like it

8. Wave Properties
Frequency: number of wavelengths that pass a fixed point each second
Count the # of crests or the # of compressions
Unit: Hertz (Hz) = 1/s = s-1
Period: amount of time it takes one wavelength to pass Unit: second

9. Wavelength vs. Frequency
Long wavelength = low frequency
Inversely related: one is up the other is down

10. Wave Speed Depends on the medium it is traveling through
Sounds: faster in liquids and solids or warmer air
Light: slower in liquids and solids

11. Calculating Wave Speed
speed(m/s)=frequency(Hz)xwavelength(m)
c = v 

12. Calculations
A wave has a frequency of Hz and a wavelength of 3.0m. What is the speed of wave?
What is the wavelength of a wave that has a frequency of 20.0 Hz and a speed of 340 m/s?

13. Amplitude and Energy
Amplitude: related to the energy carried by the wave
High amplitude = High energy

14. Amplitude and Energy
Compressional Amplitude  denser the compressions = higher amplitude

15. The Behavior of Waves
Chapter 10 Section 3

16. Reflection A wave strikes an object and bounces back
All waves can reflect
Echoes – sounds waves
reflecting

17. Law of Reflection Incidence beam and reflected beam
Normal line – perpendicular to mirror
Def: angle of i and angle of r are equal

18. Refraction Light travels at different speeds in different mediums
Change speed – change angle
Def: bending of a wave caused by change in speed from one medium to another

19. Refraction Slower in water – bends towards normal
Faster in air – bends away from normal

20. Refraction
Objects in water are farther than they appear!

21. Diffraction
Def: object causes a wave to change direction and bend around it
Diffraction – around an object
Refraction – through an object

22. How much Diffraction? Obstacle smaller than wavelength – waves bend
Obstacle larger than wavelength – waves not affected much
Hear sounds from room before see light from room
Sound waves close to size of door – bend around door
Light – too small doesn’t diffract and bend

23. Diffraction of Radio Waves
AM – longer waves – diffracted much easier – travel farther distances
FM – smaller waves – aren’t affected as much – don’t go as far

24. Interference
Def: when two or more waves combine and form a new wave

25. Constructive Interference
Waves ADD together – crests arrive at same place at same time
Amplitude = sum of two

26. Destructive Interference
Waves SUBTRACT each other – one crest meets with one trough
Amplitude – difference of two

27. Standing Waves
Def: wave pattern when waves of same wavelength and amplitude meet from opposite directions
Crest/Crest = amplitude Crest/Trough = node
Wave “stands still” because it appears to not move - vibrates

28. Resonance Objects have own natural frequencies
Depends on size, shape, material, etc.
Def: object is made to vibrate by absorbing at its natural frequency
Object absorbs more energy – higher amplitude – could break apart
Tacoma Narrows Bridge

29. Electromagnetic Spectrum
Chapter 12 Section 2
Electromagnetic Spectrum

30. What are Electromagnetic (EM) Waves?
Def: vibrating electric charges and can travel through space with no matter

31. Range of Frequencies EM waves have WIDE range of frequencies
The range = Electromagnetic Spectrum

32. Radio Waves All around you – can’t see or hear them
Sound = compressional wave
Radio = transverse
Radio: wavelengths 1 mm or longer

33. Microwaves – Type of Radio Wave
Def: wavelengths less than 1m
Wavelengths of 1cm – 10cm used for cell phones and satellites
Microwave ovens?
Vibrate water molecules – friction = thermal energy

34. Radar Radio detecting and ranging
Send radio wave and measure how long it takes to bounce back – location is found

35. Magnetic Resonance Imaging (MRI)
Developed in 1980s
Cylinder – powerful magnet, radio wave emitter and detector
p+ in H atom align to magnet
Radio waves cause p+ to flip
Flipping releases radiant energy
Radio detector reads energy – maps your insides

36. Infrared Waves Warmth – transmitted by IR waves
Def: wavelengths 1mm – 750 billionths of meter
Remotes for TVs – computers reading CD-ROMS
Hotter objects – shorter wavelengths – IR imaging

37. Visible Light
ROY G BIV
Only form can detect with eyes (rods and cones)
Def: wavelengths 750 billionths to 400 billionths of meter
Eyes pick up different wavelengths = color
Red – long wave
Violet – short wave

38. Ultraviolet Waves
Def: wavelengths 400 billionths to 10 billionths of a meter
Bad = enter skin cells = wrinkles or cancer
UVA – longer waves than UVB (sunburn)
Good = allows body to make vitamin D
Good = kills bacteria – damage cells = death

39. Ozone Layer Ozone = O3 Constantly formed and destroyed by UV waves
Destroyed by CFCs – 1 Chlorine atom can destroy thousands of O3

40. X-rays and Gamma Rays Smallest wavelengths highest frequencies
X-rays: wavelengths of 10 billionths to ten trillionths of a meter
Images of bones, bags in airport
Gamma Rays: wavelengths shorter than 10 trillionths of a meter
Produced in nuclei of atoms
X-rays and Gamma Rays used in radiation therapy – kill healthy and diseased cells

41. Chapter 12 Section 3
Radio Communication

42. Radio Transmission Radio waves vibrate e- in radio antenna.
E- produce electric current carries info
Amplifier boost current and sends to speakers to vibrate  ears  brain
Each station = certain frequency = carrier wave
Carrier wave is modified to send info

43. AM radio
AM varies the amplitude of carrier wave – Amplitude Modulation
Changing amp – speakers vibrate
540,000 – 1,600,000 Hz
Measured in kHz

44. FM Radio
FM varies the frequency of carrier wave – Frequency Modulation
Strength is constant = clearer sound
88 mil – 108 mil
Measured in MHz

45. Frequency Usage

46. Television Radio and TV both use carrier waves
Audio – FM signal Pics – AM signal
Pictures formed by cathode-ray tube – sealed vacuumed tube with 1 or more beams of e- produced
Color TV – 3 beams of e- directed at screen with magnetic field

47. Television
Screen has over 100,000 rectangular spots that glow red, green or blue when struck
Makes image when 3 beams sweep over screen – control color and brightness of each spot

48. Telephones
Sound waves in microphone  electrical signal (radio wave) microwave tower
Cell phone uses one signal to send info another signal to receive
Each base covers cell – move from cell to cell – automatically transfers signal

49. Cordless Phones
Transceiver – transmits one signal and receives another from a base unit
Using dif frequencies allows you to talk and listen at the same time

50. Satellites Satellite Telephones – can make calls over the world
Phone – satellite – ground station – phone
Long delays
Satellite TV – high frequency microwaves rather than radio waves
Why are dishes curved?
To direct waves to antenna

51. Global Positioning System (GPS)
Def: satellites, ground stations, and receivers give your exact location
Satellites owned by US Dept. of Defense – signals used by anyone