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Waves Chapters 10 & 12. The Nature of Waves Chapter 10 Sections 1 & 2.

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Presentation on theme: "Waves Chapters 10 & 12. The Nature of Waves Chapter 10 Sections 1 & 2."— Presentation transcript:

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 Def: a repeating movement that transfers energy through matter Types of waves: Types of waves: Transverse: matter (up/down) moves at right angles with the wave (left/right) 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 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 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 Frequency: number of wavelengths that pass a fixed point each second Count the # of crests or the # of compressions Count the # of crests or the # of compressions Unit: Hertz (Hz) = 1/s = s -1 Unit: Hertz (Hz) = 1/s = s -1 Period: amount of time it takes one wavelength to pass Unit: second Period: amount of time it takes one wavelength to pass Unit: second

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

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

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

12 Calculations A wave has a frequency of Hz and a wavelength of 3.0m. What is the speed of wave? 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? 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 Amplitude: related to the energy carried by the wave High amplitude = High energy High amplitude = High energy

14 Amplitude and Energy Compressional Amplitude  denser the compressions = higher amplitude 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 A wave strikes an object and bounces back All waves can reflect All waves can reflect Echoes – sounds waves Echoes – sounds waves reflecting reflecting

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

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

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

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

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

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

23 Diffraction of Radio Waves AM – longer waves – diffracted much easier – travel farther distances AM – longer waves – diffracted much easier – travel farther distances FM – smaller waves – aren’t affected as much – don’t go as far 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 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 Waves ADD together – crests arrive at same place at same time Amplitude = sum of two Amplitude = sum of two

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

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

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

29 Chapter 12 Section 2 Electromagnetic Spectrum

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

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

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

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

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

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

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

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

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

39 Ozone Layer Ozone = O 3 Ozone = O 3 Constantly formed and destroyed by UV waves Constantly formed and destroyed by UV waves Destroyed by CFCs – 1 Chlorine atom can destroy thousands of O 3 Destroyed by CFCs – 1 Chlorine atom can destroy thousands of O 3

40 X-rays and Gamma Rays Smallest wavelengths highest frequencies Smallest wavelengths highest frequencies X-rays: wavelengths of 10 billionths to ten trillionths of a meter X-rays: wavelengths of 10 billionths to ten trillionths of a meter Images of bones, bags in airport Images of bones, bags in airport Gamma Rays: wavelengths shorter than 10 trillionths of a meter Gamma Rays: wavelengths shorter than 10 trillionths of a meter Produced in nuclei of atoms Produced in nuclei of atoms X-rays and Gamma Rays used in radiation therapy – kill healthy and diseased cells 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. Radio waves vibrate e - in radio antenna. E - produce electric current carries info E - produce electric current carries info Amplifier boost current and sends to speakers to vibrate  ears  brain Amplifier boost current and sends to speakers to vibrate  ears  brain Each station = certain frequency = carrier wave Each station = certain frequency = carrier wave Carrier wave is modified to send info Carrier wave is modified to send info

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

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

45 Frequency Usage

46 Television Radio and TV both use carrier waves Radio and TV both use carrier waves Audio – FM signal Pics – AM signal Audio – FM signal Pics – AM signal Pictures formed by cathode-ray tube – sealed vacuumed tube with 1 or more beams of e - produced 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 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 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 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 Sound waves in microphone  electrical signal (radio wave)  microwave tower Cell phone uses one signal to send info another signal to receive Cell phone uses one signal to send info another signal to receive Each base covers cell – move from cell to cell – automatically transfers signal 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 Transceiver – transmits one signal and receives another from a base unit Using dif frequencies allows you to talk and listen at the same time Using dif frequencies allows you to talk and listen at the same time

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

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


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