Presentation on theme: "Waves carry energy from one place to another."— Presentation transcript:
1 Waves carry energy from one place to another. Waves have characteristic properties that do not depend on the type of wave.1234567Waves carry energy from one place to another.Transverse and longitudinal waves exist in mechanical media, such as springs and ropes, and in the Earth as seismic waves.Wavelength, frequency and wave speed are related.Sound is a longitudinal wave whose speed depends on the properties of the medium in which it propagates.Radio waves, light and X-rays are different wavelength bands in the spectrum of electromagnetic waves, the speed of which in a vacuum is approximately 3 x 108m/s, and less when passing through other media.Waves have characteristic behaviors, such as interference, diffraction, refraction and polarization.Beats and the Doppler Effect result from the characteristic behavior of waves.
2 Are these the same things? What are they?Are these the same things?Radio WavesMicrowavesInfraredVisible LightUltraviolet LightX-raysGamma RaysBefore we answer that question, lets review some metric units & scientific notation.
3 normal units without prefixes SymbolValueDescriptionpicop10-121 picometer, (pm) = mnanon10-91 nanometer, (nm) = mmicroµ or u10-61 micrometer (µm) = mmillim10-31 millimeter (mm) = mcentic10-21 centimeter (cm) = 0.01 mdecid10-11 decimeter (dm) = 0.1 mNONE1normal units without prefixeskilok1031 kilohertz (kHz) = 1000 HzmegaM1061 megahertz (MHz) = 1,000,000 HzgigaG1091 gigahertz (GHz) = 1,000,000,000 HzteraT10121 terahertz (THz) = 1,000,000,000,000 Hz
4 Are all parts of the electromagnetic spectrum Radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays Are all parts of the electromagnetic spectrumand are fundamentally the same thing.They are all electromagnetic radiation.The electromagnetic spectrum can be expressed in terms of wavelength, frequency, or energy.
5 v = f x λ v = f x λ 340 m/s = speed of sound 300,000,000 m/s = speed of light3*108 m/s = 3*105 Hz x 1*103 mv = f x λ
6 v = f x λ c = 3×108 m/s (Approximate Value) 340 m/s = speed of sound300,000,000 m/s = speed of lightc = 3×108 m/s (Approximate Value)Speed of light in a vacuum 299,792,458 m/s (1,079,252,849 km/h)
7 Lower Energy Higher Energy Energy E = h x f (Planks Constant) h = 6.626 × 10-34 joule·seconds h = x eV·seconds1 eV = ×10−19 J.
8 Energy in Electro Magnetic Waves E = h x fh = 6.626 × 10-34 J·sec (Planks Constant)EM WaveFreq (Hz)h x f = EEnergyTelevision108 Hz(6.626 x 10-34) x (108)6.6 x10-26 JInfrared1014 Hz(6.626 x 10-34) x (1014)6.6 x10-20 JUltra Violet1016 Hz(6.626 x 10-34) x (1016)6.6 x10-18 JX-Rays1018 Hz(6.626 x 10-34) x (1018)6.6 x10-16 JWhat about a Microwave at 3,000 MHz (3.0 x 109 Hz)?
9 E = h x f KE = ½ mv2 994,000 J = ½ * 1179 Kg * 41 m/s If a single microwave (photon) has a frequency of 3,000 MHz, how much energy will it have?E = h x fh = 6.626 × 10-34 J·secE = (6.626 × 10-34 J·sec) x (3.0 x 109 Hz)E = 1.99 x J per photonEM(Hz)EnergyTV108 Hz6.6 x10-26 JIR1014 Hz6.6 x10-20 JUV1016 Hz6.6 x10-18 JX-Rays1018 Hz6.6 x10-16 JNOTE: a 1KW microwave oven with a frequency of 2999 MHz produces 5.0 x 1029 photons per second.E = (1.99 x J) x (5.0 x 1029)= 994,000 J per secondKE = ½ mv2Note: most microwaves operate at 2,450 MHz not 2,999 MHz994,000 J = ½ * 1179 Kg * 41 m/s994,000 J = ½ * Toyota * 90 mph
10 Radio Waves - Longest wavelengths in the EM spectrum Cellular100 kHz1 GHzWaves can be longer than a ten football fields or as short as a football.Radio waves can penetrate the earths atmosphere – radio astronomyThe above image shows the Carbon Monoxide (CO) gases in our Milky Way galaxy.
11 Radio Waves - Common frequency bands include the following: -AM radio kilohertz to 1.7 megahertz-Short wave radio - bands from 5.9 megahertz to 26.1 megahertz-Citizens band (CB) radio megahertz to megahertz-Television stations - 54 to 88 megahertz for channels 2 through 6-FM radio - 88 megahertz to 108 megahertz-Television stations to 220 megahertz for channels 7 through 13Every wireless technology you can imagine has its own little band:-Garage door openers, alarm systems, etc. - Around 40 megahertz-Standard cordless phones: Bands from 40 to 50 megahertz-Baby monitors: 49 megahertz-Radio controlled airplanes: Around 72 megahertz, which is different from...-Radio controlled cars: Around 75 megahertz-Wildlife tracking collars: 215 to 220 megahertz-MIR space station: 145 megahertz and 437 megahertz-Cell phones: 824 to 849 megahertz-New 900-MHz cordless phones: Obviously around 900 megahertz!-Air traffic control radar: 960 to 1,215 megahertz-Global Positioning System: 1,227 and 1,575 megahertz-Deep space radio communications: 2290 megahertz to 2300 megahertz
12 Radio Waves - Longest wavelengths in the EM spectrum
13 Radar is an acronym for "radio detection and ranging" 100 kHz1 GHzCentimetersMicrowave OvensMicrowaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds, and smoke.(point - to - point)Shorter microwaves are used in remote sensing. These microwaves are used for radar like the doppler radar used in weather forecasts. Microwaves, used for radar, are just a few inches longRadar is an acronym for "radio detection and ranging"
14 1 x1012 Hz4 x1014 Hz750 nmSpecial cameras and film that can detect differences in temperature, and then assign different brightnesses or false colors to them.Far infrared waves are thermal. In other words, we experience this type of infrared radiation every day in the form of heat ! The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infraredShorter, near infrared waves are not hot at all - in fact you cannot even feel them. These shorter wavelengths are the ones used by your TV's remote control.
15 Which EM wavelengths can make it through our Atmosphere? H e a t
16 Visible light can easily penetrate the atmosphere, Infrared can not penetrate (or escape) as easily.
17 ColorWavelengthviolet380–450 nmblue450–495 nmgreen495–570 nmyellow570–590 nmorange590–620 nmred620–750 nmThough electromagnetic waves exist in a vast range of wavelengths, our eyes are sensitive to only a very narrow band – visible light (approximately 400 – 700 nm)
18 1 x1015 Hz3 x1016 HzThough these waves are invisible to the human eye, some insects, like bumblebees, can see them!400 nm10 nmUVA 400 nm – 315 nm (Black Lights)UVB 315 nm – 280 nm (Sun Burn)UVC 280 nm – 100 nm (germicidal)Health concerns for UV exposure are mostly for the range nm in wavelength, the range called UVB. The most effective biological wavelength for producing skin burns is 297 nmA sterilization method that uses ultraviolet (UV) light to break down micro-organisms. (Food, air and water purification.)
19 We usually talk about X-rays in terms of their energy rather than wavelength. 1 x1016 Hz1 x1018 HzBecause your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent. Metal absorbs even more X-rays.Many things in space emit X-rays, among them are black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun, and even some comets!
20 Many things in deep space give off X-rays Many things in deep space give off X-rays. Many stars are in binary star systems - which means that two stars orbit each other. When one of these stars is a black hole or a neutron star, material is pulled off the normal star. This materials spirals into the black hole or neutron star and heats up to very high temperatures. When something is heated to over a million degrees, it will give off X-rays!The above image is an artist's conception of a binary star system - it shows the material being pulled off the red star by its invisible black hole companion and into an orbiting disk.
21 1 x1018 HzThese waves are generated by radioactive atoms and in nuclear explosions.Smallest wavelengths and the most energy of any other wave in the Electromagnetic spectrum.Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells.
22 v = f x λ E = h x f Gamma Rays – ENERGITICALLY Interesting Facts Gamma-ray bursts can release more energy in 10 seconds than the Sun will emit in its entire 10 billion-year lifetime! So far, it appears that all of the bursts we have observed have come from outside the Milky Way Galaxy. The sources of these enigmatic high-energy flashes remain a mystery.Smallest wavelengthsHighest frequencyMost energyv = f x λE = h x fBy solving the mystery of gamma-ray bursts, scientists hope to gain further knowledge of the origins of the Universe, the rate at which the Universe is expanding, and the size of the Universe.
23 LIGHT LIGHT LIGHT Visible Light What is the only thing that we (humans) can see?A very small band of the electromagnetic spectrum between 380 – 750 nm (400 – 700 nm)LIGHT
24 Sight & LightWhat is occurring between our eyes and the objects that we see?Is there anything traveling between our eyes and the objects?Rods & Cones send signals to the brain
25 What do you see? WAIT - Don’t say it out loud. An electromagnetic wave with a wavelength of approx. 600 nm
26 All visible wavelengths What do the EM waves do when they hit an object?White LightAll visible wavelengthsUntil the EM waves hit an objectEnergy traveling as EM waves through a medium (or a vacuum)
27 We see the wavelengths of light that are reflected off of the object. The wavelengths of light we seeWe see the wavelengths of light that are reflected off of the object.All other wavelengths are absorbed by the object.Daylight -Not a perfect spectrumReflected light
28 Do we see all of wavelengths of visible light at the same intensity? Color absorption by different glass
29 Did the actual paint on the walls change? Incandescent bulbDaylight bulbMercury LampDid the actual paint on the walls change?Sodium Lamp (low pressure)Sodium Lamp (high pressure)
30 What are the wavelengths of these spectral lines? What is the perceived color of the light source?What are the wavelengths of these spectral lines?Neon SpectrumPerceived color VS actual wavelengths present in the light source.Not every wavelength presentSpectral lines
31 Today’s LabDetermine the wavelengths that are present in six different light sources|||||||||||||||||||||||||||||||||||||||||| | | | || | | | | | | | ||||||||||||||||||||||||||||||||||||||||||| | | | || | | | | | | | |Lab ReportBlueDark RedYellow/Orange
32 Visible Light & Wavelength Wave speed did not change Let us return to the lab we did last class
33 Colors of Light G R B R + G B + G R + B Green – Magenta Red – Cyan Simulation – mixing colors of light (over lapping)GRBR + GB + GR + BGreen – MagentaRed – CyanBlue – Yellow
34 Note that the intensity (the brightness) of each band is different Helium Spectral Lines – Lab ResultsPerceived color = pink?|||||||||||||||||||||||||||||||||||||||||| | | | || | | | | | | | ||||||||||||||||||||||||||||||||||||||||||| | | | || | | | | | | | |Note that the intensity (the brightness) of each band is different
35 Fluorescent Tube Spectral Lines - Results Hallway Fluorescent lightsNote the differences in intensity
36 Natural Light (sun light on sky bridge) 400 nm700 nmIncandescent Bulb (night light)Fluorescent Bulb - older type - (single tube)Fluorescent Bulb - Newer type - (hallway lights)Fluorescent Bulb - Energy Saver - (not in class)
41 h = 6.626 × 10-34 J·sec (Planks Constant) E = h x f 400 nm nm nm nmE = h x fColorWavelength (nm)h x f = EViolet(6.626 x 10-34) x (1.36 x Hz)(6.626 x 10-34) x (1.45 x Hz)Bluegreen (cyan)(6.626 x 10-34) x (1.62 x Hz)Red(6.626 x 10-34) x (2.19 x Hz)(6.626 x 10-34) x (2.19 x Hz)
46 Slowing down and changing the direction of light Degree of Scattering
47 Slowing down and changing the direction of light Selective ScatteringDegree of Scattering
48 Why… I need some new/better PPT slides to explain why… Is the sky blue?Are clouds white/gray?Is the ocean blue/green?Are sunsets red/golden?
49 Chose One: Include: HOMEWORK: Designing new PowerPoint Slides blue-sky, white clouds, blue/green oceans, red sunsetsInclude:1- How sunlight is a combination of all wavelengths (colors) of light2- Which EM wavelengths/frequencies are involved (how)3- How light is absorbed, reflected, scattered, etc.4- What is occurring at the atomic level (Absorption & Emission)Chapters 27 & 28 – Sections 27.4, 27.5, 28.3, 28.7 – 28.10On the computer OR hand drawn
50 Unpolarized Light - waves vibrating in more than one plane Electric charges vibrate in a variety of directions, thus creating an electromagnetic wave which vibrates in a variety of directions.Unpolarized Light - waves vibrating in more than one planePolarized light - waves vibrating in a single plane.PolarizedUnpolarizedUnpolarizedUnpolarized
51 Polarization – process of transforming unpolarized light into polarized light. (Filter)
52 Using two polarization filters Polarization axis alignedPolarization axis perpendicularTwo Polarization filter - simulation
53 Polarization by reflection Glare from the RoadRemoving the Glare
54 QuestionConsider the three pairs of sunglasses below. Identify the pair of glasses is capable of eliminating the glare resulting from sunlight reflecting off the calm waters of a lake? _________ (The polarization axes are shown by the straight lines.)3-D Glasses
55 Incident Ray - the ray of light approaching the mirror Reflected Ray - the ray of light which leaves the mirrorThe Normal - an imaginary line perpendicular to mirrorAngle of Incidence - the angle between the incident ray and the normalAngle of Reflection - the angle between the reflected ray and the normalThe law of reflection - when a ray of light reflects off a surface the angle of incidence is equal to the angle of reflectionN
56 Question1. Consider the diagram above. Which one of the angles (A, B, C, or D) is the angle of incidence? ______2. Which one of the angles is the angle of reflection? ______
57 QuestionA ray of light is incident towards a plane mirror at an angle of 30-degrees with the mirror surface. What will be the angle of reflection?
58 Scatters Light in all directions Reflection off of different types of surfacesScatters Light in all directionsSpecular reflection - Reflection off of smooth surfaces such as mirrors or a calm body of waterDiffuse reflection - Reflection off of rough surfaces such as clothing, paper, and the asphalt roadway
60 What if the Blue floor had a rougher texture? The law of reflection - the angle of incidence is equal to the angle of reflection (when a ray of light reflects off a surface).Reflection off different types of surfacesWhat if the Blue floor had a rougher texture?
61 Reflection of waves --- More than just light Echoes - when a reflected sound wave reaches the ear more than 0.1 seconds after the original sound wave was heard.> 17 mReverberations - the prolonging of a sound. The reception of multiple reflections off of walls and ceilings within (less than) 0.1 seconds of each otherSince sound waves travel at about 340 m/s at room temperature, it will take approximately 0.1 s for a sound to travel the length of a 17 meter room and back, thus causing a reverberation
62 Reflection of waves --- More than just light Radar
63 Reflection of waves --- More than just light Focusing wavesSmooth walls direct sound waves in a specific direction.Rough walls tend to diffuse sound, reflecting it in a variety of directions. This allows a spectator to perceive sounds from every part of the room, making it seem lively and full.
64 The speed of a wave is determined by the medium Boundary - When one medium ends, another medium begins; and the behavior of a wave at that boundary is described as its boundary behavior.Change of medium at the boundaryThe speed of a wave is determined by the mediumSlows DownSpeeds Up
65 The boundary behavior of waves - summarized 1- the wave speed is always greatest in the least dense medium2- the wavelength is always greatest in the least dense medium3- the frequency of a wave is not altered by crossing a boundaryFasterSlowerSlowerFasterGreater λSmaller λSmaller λGreater λFrequency does not changeFrequency does not change
66 QuestionA pulse in a more dense medium is traveling towards the boundary with a less dense medium.The speed of the pulse in the less dense medium will be _______ (greater than, less than, the same as) the speed of the incident pulse coming from the more dense medium.2. The wavelength of the pulse in the less dense medium will be _______ (greater than, less than, the same as) the wavelength of the incident pulse coming from the more dense medium.3. The frequency of the pulse in the less dense medium will be _______ (greater than, less than, the same as) the frequency of the incident pulse coming from the more dense medium.
68 Finish Start Higher Density = Slower wave speed Densest Denser Dense Minuscule amount of time before releaseMinuscule amount of time before releaseSpeed of LightSpeed of LightSpeed of LightHigher Density = Slower wave speedStartFinishPhotonDenseDenserDensestPhotonPhoton
70 -Caused by a change in speed and wavelength of the waves Reflection - change in direction of waves when they bounce off a barrier.Refraction change in the direction (bending) of waves as they cross from one medium to another.-Caused by a change in speed and wavelength of the wavesRefraction – wave frontsAir Less Dense FasterGlass More Dense SlowerRefraction (bending) only occurs at the boundary.
71 The boundary behavior of waves - summarized 1- the wave speed is always greatest in the least dense medium2- the wavelength is always greatest in the least dense medium3- the frequency of a wave is not altered by crossing a boundaryMore Dense = greater angleFasterSlowerSlowerFasterGreater λSmaller λSmaller λGreater λFrequency does not changeFrequency does not changeRefraction Index simulator - including refraction of individual wavelengths
72 The amount by which light slows (and therefore bends) in a given material is described by the index of refractionn = c/vDense SlowDenser SlowerDensest SlowestmaterialnVacuum1Crown Glass1.52Air1.0003Salt1.54Water1.33Asphalt1.635Ethyl Alcohol1.36Heavy Flint Glass1.65Fused Quartz1.4585Diamond2.42Whale Oil1.460Lead2.6More dense More bendingRefraction Index, Total Internal Reflection, and Critical Angle Simulation
73 --Depends upon the Angle of Incidence & the medium density Total Internal Reflection (TIR) - when the angle of incidence is greater than the critical angle, no refraction occurs.--Depends upon the Angle of Incidence & the medium densityRefractive IndexCritical AngleThe Sparkle of Diamonds – All incoming light can only exit the diamond out of the top of the gem
74 Total Internal Reflection Reflection at the Critical Angle (Total Internal Reflection)Critical Angle - The largest angle of incidence for which refraction can still occur.The angle of incidence yields an angle of refraction of 90-degrees.For any angle of incidence greater than the critical angle, light will undergo total internal reflection (TIR).RefractionCritical AngleTotal Internal ReflectionCritical Angle of Reflection Simulation
75 Dispersion - the separation of visible light into its different colors Refraction simulator including individual wave lengthsDrop of water
77 Rainbows – Refraction, Dispersion, Reflection Bending of light Color Separation Direction ChangeWhite lightAirH2O-Incident white light contains all wavelengths -Some of the light is reflected-The rest of the light is refracted -Light splits (dispersion) into component colors -Reflected at rear of raindrop (TIR – Total internal Reflection) -Refracted again as it leaves raindrop-Colors are further dispersed
80 Greater angle of incidence = greater angle of refraction
81 Opening Boundary Diffraction Refraction Diffraction - a change in direction of waves as they pass through an opening or around an obstacle in their path. (not across a boundary/medium change)OpeningBoundaryRefractionDiffraction
82 Diffraction - a change in direction of waves as they pass through an opening or around an obstacle in their path. (not across a boundary/medium change)
83 Reflection - change in direction of waves when they bounce off a barrier. (Also total interior reflection - TIR)Refraction - change in the direction of waves as they pass from one medium to another.Diffraction - change in direction of waves as they pass through an opening or around an obstacle in their path.Interference
85 Constructive interference occurs wherever a thick line meets a thick line or a thin line meets a thin line; this type of interference results in the formation of an antinode. Destructive interference occurs wherever a thick line meets a thin line; this type of interference results in the formation of a node.. `