C hapter 25 Introduction to Waves Part 1 In most simple terms a wave is defined as a disturbance When a wave is transmitted the material that is being disturbed is the medium Medium a solid liquid or gas that waves travel through The medium that creates the wave does not move the wave There are several parts to a wave Crest the mountain Trough the valley o These two together create a cycle Wavelength the length of one cycle Amplitude the height of the wave Wave period the time it takes the medium to vibrate through one cycle Frequency number of cycles per second o Measured in Hertz Waves do not undergo any net movement There are two types of waves the wave is moving Transverse waves When the medium vibrates at right angles to the direction o Examples Water waves light waves rope waves Longitudinal compression waves When the medium vibrates back and forth parallel to the direction the wave is moving o Examples Sound waves SOUND WAVES TRAVEL THROUGH AIR AT ABOUT 1100 FEET PER SECOND Objects travelling faster than the speed of sound will produce a wave called a sonic boom Shock waves When waves in front of an object are bunched together because the object is moving faster than the waves can be transmitted Example Boat waves Chapter 26 Introduction to Waves Part 2 Sound can travel in any solid liquid or gas but NOT a vacuum Humans have a hearing range of 20 to 20 000 Hz Ultrasonic waves any frequency above 20 000 Hz o Examples of ultrasonic sounds sonar bug deterrent clean jewelry medicine burglar alarm Resonant frequency the natural oscillation back and forth of an object The more mass in an object the lower its frequency People are able to break glasses with their voices when the singer s voice matches the resonant frequency of the glass Two ways to get an object to resonate o Tap it o Place a sound nearby that is resonating at the natural frequency of the object Chapter 27 Electromagnetic Waves light Electromagnetic EM wave double transverse wave Travels through a vacuum at 186 282 miles per second Fastest wave known and is the only wave that can travel through an empty space Because a wave is defined as a disturbance what exactly is being disturbed when light travels through a vacuum Scientists answered this question in the 19th century by proposing the existence of an ether o Ether an invisible and massless which filled the voids of space o This was proven as incorrect James Clerk Maxwell introduced ideas that explained the phenomena of light Don t need an ether Light is a force of nature Move a charged particle an electron ad it will emit a force field into space like a whole o Known as The Theory of Magnetism Of the 8 types of EM waves humans can see only 1 the visible light waves The visible light waves can be remembered by ROY G BIV Light waves have a range of 400 750 Hz also known as cycles per second o 400 450 trillion red o 450 500 trillion orange o 500 550 trillion yellow o 550 600 trillion green o 600 650 trillion blue o 650 700 trillion indigo o 700 750 trillion violet White and black are not a single color o White the combination of red green and blue o Black When there is no visible light Chapter 28 The Electromagnetic Spectrum The electromagnetic spectrum all of the electromagnetic waves in order from lowest to highest frequency Radio waves o 0 2 billion Hz o Change the size of a wave amplitude modulation also known as AM o Change the frequency frequency modulation also known as FM Microwave waves o 2 100 billion Hz Heat waves Infrared waves o 100 billion 10 trillion Hz o Sun s immediate warmth o Used to cook food o 10 trillion 400 trillion Hz o Used to warm food o Causes sunburn o Bodies radiate infrared Visible light waves o 400 trillion 750 trillion Hz o ROY G BIV Ultraviolet waves o 750 100 000 trillion Hz o Can damage destroy cells o Atmosphere absorbs 98 of UV Xray waves o 100 10 000 000 trillion Hz o Discovered by Roentgen Gamma rays o 10 000 000 trillion o Believed that gamma ray bursts have affected evolution o Created in deep space Colliding galaxies What moves faster a light wave or a gamma wave They move at the same speed the speed of light the difference is their frequency Chapter 29 Coherent Light and Laser There are twelve wave occurrences that will be discussed from chapters 29 34 Each will be underlined for clarification The first is luminosity Luminosity Process where electromagnetic waves light are produced Produced four different ways o Heat o Passing charged particles through gas o Chemical reaction Seen in lightning bug and deep water fish o Nuclear reaction Incoherent light When waves don t exactly match up with one another One wave may be going through a crest while another goes through the trough Coherent light Light waves that align with one another potentially exerting a large force on an object Examples o Light amplification by the stimulated emission of radiation LASER Can be used for medical purposes and in holograms Chapter 30 Reflection Transmission and Absorption The second of the twelve wave occurrences is reflection Reflection When a wave hits an object and then is returned Incident wave The wave that hits an object Reflected wave The wave that bounces off an object o The angle of incident I is equal to the angle of reflection R Objects reflect less than 100 of the light that shines upon them Fiber optics can reflect virtually all light o Used in medicine communication and decorative lamps Reflection is frequency dependent which is why we see certain color s upon reflection The material keeps the color we see and reflects the others When a piece of paper reflects a light wave of 400 trillion Hz it appears red Theoretically a piece of red paper is warmer than a piece of blue paper Light can scatter two different ways when it is being reflected Specular reflection An even mirror reflection a Diffuse reflection Uneven scattered reflection b If a wave isn t reflected it can be absorbed the third of the twelve wave occurrences Absorption When light is kept by a surface and changed to heat o Why black clothing feels warmer than white clothing when worn in the sun White clothing reflects light waves while black absorbs them If a wave isn t reflected or absorbed it is transmitted the fourth of the twelve wave occurrences Transmission When a wave passes through the object o Opaque when no light passes through o Translucent when some light passes through Chapter 31 Phosphorescence Fluorescence and Doppler Effect The fifth of the twelve