Chapter 8 WAVES— SOUND AND LIGHT

1 Chapter 8 waves SOUND AND LIGHT Vibrations and waves Wave Motion Transverse and Longitudinal waves The Nature of SOUND Resonance The Nature of LIGHT Reflection Transparent and Opaque Materials Color Refraction Diffraction Interference The Doppler Effect The Wave Particle DualityIn this unit, we will look at:I can define what a wave is, list several different types of waves and compare a wave with a Goal:Vibration:a wiggle in timeWave:a wiggle in space and time a disturbance that travels from one place to another transporting and waves DemonstrationDescription: Vibrationin terms of frequency (time) how often vibration motion occurs Wavein terms of its frequency, speed, amplitude, and wavelengthVibrations and WavesFrequency:number of to-and-fro vibrations in a given timeUnit: 1 vibration per second = 1 HertzPeriod:defined as the time it takes for a complete vibrationUnit: any unit of time, usually secondsVibrations and WavesRelationship between frequency and period:Frequency = 1/period Unit: Hertz (Hz)Period = 1/frequency Unit: second (s)The source of all waves is a and than 20 of the the frequency of a particular wave is 20 Hz, its period isVibrations and WavesCHECK YOUR :Note when = 20 Hz, T= 1/ = 1/(20 Hz) = 1 the frequency of a particular wave is 20 Hz, its period isVibrations and WavesCHECK YOUR ANSWER The propagation of a disturbancethrough a medium The medium transporting the wave returns to initial condition after disturbance has passed Requires an energy source and a medium (except for LIGHT ) through which the energy is transferredWave MotionWave characteristics.

2 Crest highest point Trough lowest pointWavelength AmplitudeFrequency PeriodWave MotionA. distance between adjacent peaks in the direction of travel for a transverse wave is itsWave MotionCHECK YOUR NEIGHBORC. :The wavelength is the distance between any adjacent identical parts of the distance between adjacent peaks in the direction of travel for a transverse wave is itsWave MotionCHECK YOUR ANSWERWave speed: describes how fast the disturbance moves through the medium related to frequency and wavelengthEquation for wave speed:Wave speed = frequency wavelengthv= Wave MotionTwo different types of waves classified in the direction in which the medium vibrates compared to the direction of energy travel: Longitudinal wave: the vibration is in the direction of travel. Transverse wave: the vibration is in right angles (sideways) to wave and Longitudinal WavesLongitudinal wave Transverse waveTransverse and Longitudinal WavesA.

3 Along the to the of the of the vibrations along a transverse wave move in a directionTransverse and Longitudinal WavesCHECK YOUR NEIGHBORB. perpendicular to the :The vibrations in a longitudinal wave, in contrast, are along (or parallel to) the direction of wave vibrations along a transverse wave move in a directionTransverse and Longitudinal WavesCHECK YOUR ANSWERI can define what a wave is, list several different types of waves and compare a wave with a Goal:End Day 1 SOUND WavesHomework ReviewI can calculate wave properties in terms of frequency, wavelength, wave speed, and Goal: and WavesEnd of Day 2 waves and LightI can calculate wave properties in terms of frequency, wavelength, wave speed, and Learning than 20 of the a wave machine is generating a wave by making 20 vibrations per second, the frequency isWave than 20 of the a wave machine is generating a wave by making 20 vibrations per second, the frequency isWave ReviewFor this wave, the wavelength is shown by:ABCAny of the linesWave ReviewABCFor this wave, the wavelength is shown by:ABCAny of the linesWave ReviewABCWave t determine with the information a wave with a frequency of 10 Hertz, a period of 1/10 seconds, a wavelength of 10 cm and an amplitude of 3 cm, the wave speed would be.

4 Wave t determine with the information a wave with a frequency of 10 Hertz, a period of 1/10 seconds, a wavelength of 10 cm and an amplitude of 3 cm, the wave speed would be: Wave speed = frequency x wavelengthFor this wave, the amplitude is shown by:ABCAny of the linesWave ReviewABCFor this wave, the amplitude is shown by:ABCAny of the linesWave ReviewABCH omework ReviewI can explain the nature of LIGHT in terms of wavelength and the electromagnetic Goal: LIGHT :Electromagnetic waves created by vibrating electric charges having frequencies that fall within the range of sightThe Nature of LightLight:the frequency of vibrating electrons equals the frequency of the lightThe Nature of LightLight:Travels nearly a million times faster than SOUND in airLight can travel through a vacuum!The Nature of LightLight: LIGHT and all electromagnetic waves are transverse wavesThe Nature of LightEnergyThe Electromagnetic SpectrumThe Nature of LightA.

5 Radio electromagnetic spectrum is a span of electromagnetic waves , ranging from lowest to highest frequencies. The smallest portion of the electromagnetic spectrum is that of The Nature of LightCHECK YOUR :This can be inferred by a careful study of the spectrum. The smallest portion of the electromagnetic spectrum is that ofThe Nature of LightCHECK YOUR ANSWERE lectromagnetic waves are composed of perpendicular electric and magnetic fields that vibrate perpendicular to the direction of wave travel. The Nature of LightA photographer wishes to photograph a lightning bolt by setting his camera so that it is triggered by the SOUND of Nature of LightA situation to ponder idea for nearby lightning idea for all idea for nearby lightning idea for all this a good idea or a poor idea?A situation to ponder CHECK YOUR NEIGHBOR idea for all : LIGHT travels about a million times faster than SOUND .

6 By the time the SOUND of thunder arrives, the lightning bolt is long this a good idea or a poor idea?A situation to ponder CHECK YOUR ANSWERR eflection:the returning of a wave to the medium through which it came when encountering a reflective surfaceReflectionLaw of reflection:angle of incidence = angle of reflectionReflectionDiffuse ReflectionWhen LIGHT is incident on a rough surface, it is reflected in many surface is smooth with less diffuse reflection, part of which would otherwise reach the driver s road usually means a wet road usually means more vapor in the is no reason that s just the way it with a dry road, seeing is difficult when driving at night on a wet road. Why?ReflectionCHECK YOUR NEIGHBORA. Wet surface is smooth with less diffuse reflection, part of which would otherwise reach the driver s with a dry road, seeing is difficult when driving at night on a wet road.

7 Why?ReflectionCHECK YOUR ANSWERT ransparent materials:(glass and water) LIGHT passes through in straight lines, with atoms undergoing a series of absorptions and reemissionsTransparent and Opaque MaterialsOpaque materials:colored glass is opaque to much of incident white lightTransparent and Opaque MaterialsI can explain the nature of LIGHT in terms of wavelength and the electromagnetic Goal:End of Day 3 waves and LightColorI can explain the nature of LIGHT in terms of wavelength and the electromagnetic Goal:The Electromagnetic SpectrumThe Nature of LightThe color we see depends on frequency of LIGHT ranging from lowest (red) to highest (violet). In between are colors of the FrequencyLow FrequencyHues in seven colors: Red, Orange, Yellow, Green, Blue, Indigo, and together, they add to appear ReflectionMost objects don t emit LIGHT , but reflect ReflectionA material may absorb some of the LIGHT and reflect the :PaintNatureColorSelective ReflectionDependent on the wavelengths present in the YOUR NEIGHBORG reen G is reflected because it is not absorbed so Green is seenRed R is reflected because it is not absorbed so Red is seenSelective TransmissionThe color of a transparent object depends on the color of the LIGHT it transmits (or lets pass through).

8 ColorThree types of cone receptors in our eyes perceive color each is stimulated by only certain frequencies of LIGHT : LIGHT of lower frequencies stimulates the cones sensitive to low frequencies (red) LIGHT of middle frequencies stimulates the cones sensitive to mid-frequencies (green) LIGHT of high frequencies stimulates the cones sensitive to high frequencies (blue)Vision & ColorStimulation of all three cones equally, we see white lightVision & ColorAdditive primary colors (red, blue, green):red + blue = magentared + green = yellowblue + green = cyanColorOpposites of primary colors:opposite of green is magentaopposite of red is cyanopposite of blue is yellowThe addition of any color to its opposite color results in Infrared A and A nor which is the human eye blind?ColorCHECK YOUR NEIGHBORA. Infrared A and A nor which is the human eye blind?

9 ColorCHECK YOUR ANSWERIn a vacuum (like space), all electromagnetic waves travel at the same speed: x 108 is called the Speed of LIGHT and its symbol is = frequency x wavelengthSpeed of LightIn a vacuum (like space), all electromagnetic waves travel at the same speed: x 108 is called the Speed of LIGHT and its symbol is = frequency x wavelengthSpeed of LightThe different colors of LIGHT that we see correspond to different frequencies. The frequency of red LIGHT is lower than the frequency of blue LIGHT . Because the speed of both kinds of LIGHT is the same, a lower frequency wave has a longer wavelength. A higher frequency wave has a shorter wavelength. Therefore, red LIGHT s wavelength is longer than blue LIGHT of LightColorCHECK YOUR NEIGHBORY ellow LIGHT has a longer wavelength than green LIGHT . Which color of LIGHT has the higher frequency?

10 A. have the same YOUR NEIGHBORY ellow LIGHT has a longer wavelength than green LIGHT . Which color of LIGHT has the higher frequency?A. have the same wave with a longer wavelength has lower frequency! I can explain the nature of LIGHT in terms of wavelength and the electromagnetic Goal:End of Day 4 Properties of waves andWave BehaviorI can explain the difference between refraction, diffraction and interferencein terms of wave Goal:Occurs whenever successive impulses are applied to a vibrating object in rhythm with its natural ~regesterj/potl/ waves / :the bending of a wave due to a change in themedium and/or speed of the waveRefractionRefraction occurs when SOUND waves are affected by uneven winds, or when air near the ground is warmer than air lens (a)-incoming parallel LIGHT rays refract and converge to a focal pointDiverging lens (b)-incoming parallel LIGHT rays refract in such a way that extended rays diverge to a focal point in front of the lensRefraction - LensesReflection.