electroencephalogram

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5 electroencephalogram

6 Particle Waves Electrons are STANDING WAVES in atomic orbitals. λ = h p

7 Electron Waves Probability Waves in an Ocean of Uncertainty A wave packet in a square well (an electron in a box) changing with time.

8 Super Strings

9 Waves Transmit Energy Waves transmit energy but there is not net displacement of the medium through which they travel.

10 result from periodic disturbance same period (frequency) as source Longitudinal or Transverse Waves Characterized by amplitude (distance bits of medium move from their equilibrium positions: bit of string, bird on ocean wave) 1 f = Τ periodor frequency (time for each bit to go through one cycle, up and down or to and fro.) wavelength (the distance the cycle repeats in a time freeze frame, distance peak to peak or trough to trough) wave speed (how fast is the energy transferred?) v= λ f

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12 Spherical Waves

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14 Wavelength and Frequency are Inversely related: The shorter the wavelength, the higher the frequency. The longer the wavelength, the lower the frequency. f = v λ 3Hz 5Hz

15 3Hz 5Hz

16 Wave Energy: E ~ f 6 10 ev 10 ev 4 1 2eV 40eV KeV MeV Energy to ionize atom or molecule: eV

17 Limits of Vision Electron Waves 11 λ e = 2.4x10 m

18 Types of Waves

19 Types of Waves Sound String

20 Coupled Oscillators Molecules and atoms are modeled as coupled oscillators. Waves Transmit Energy through coupled oscillators. The coupled oscillators make the medium.

21 Light is an Electromagnetic Wave Light is a Transverse Wave Light Travels in a Vacuum

22 Sound is a Longitudinal Wave Pulse Tuning Fork Guitar String

23 Quiz 1. If a water wave oscillates up and down 4 times each second and the distance between wave crests is 2m, what is its frequency? a) 1/4 Hz b) 2 Hz c) 3 Hz d) 4 Hz 2. Its wavelength? a) 1/2 m b) 2 m c) 3 m d) 4 m 3. Its wave speed? a) 2 m/s b) 4 m c) 6 m d) 8 m 4. When a fire truck moves towards you with the siren blaring, do you measure an increase or decrease in wave frequency? a) increase b) decrease c) no change 5. When a fire truck moves towards you with the siren blaring, do you measure an increase or decrease in wave speed? a) increase b) decrease c) no change

24 v = λ f

25 Wave Equation v = λ f This gives the relationship between the wavelength and frequency for constant wave speed. The frequency depends on the source and the speed depends on the properties of the medium. The speed of sound is independent of the frequency. When traveling from one medium to another, if the speed changes, the wavelength changes but the frequency remains the same.

26 Wave Speed Question Calculate the period of an ocean wave that has a wavelength of 10.0m and a wave speed of 2.00m/s. vwave = λ f 1 = λ Τ = λ / v Τ Τ= 10 m/ 2 m/ s = 5s

27 Reflect ECHO

28 Echo vs Reverberation A reverberation is perceived when the reflected sound wave reaches your ear in less than 0.1 second after the original sound wave. Since the original sound wave is still held in memory, there is no time delay between the perception of the reflected sound wave and the original sound wave. The two sound waves tend to combine as one very prolonged sound wave.

29 Diffract We can hear around corners. Why can t we see around corners? If the size of the wave (wavelength) is close in size to the object (door way) then the wave will diffract (bend).

30 Refract Sound waves refract (bend) when moving between mediums in which it travels at different speeds.

31 Waves ADD up point by point in space.

32 Superposition Waves ADD in space.

33 Superposition Spread Out in Space NON LOCAL Superposition Localized in Space LOCAL NO Superposition

34 Superposition Waves ADD in space. Simply add them point by point.

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36 Interference Waves ADD: Constructive Interference. Waves SUBTRACT: Destructive Interference. In Phase Out of Phase

37 Interference: Two Spherical Sources

38 Standing Wave: Produced by the superposition of two identical waves moving in opposite directions.

39 Transverse Standing Wave

40 Reflected PULSE: Free End Bound End

41 Standing Waves on a String Harmonics

42 Standing Waves

43 Longitudinal Standing Wave

44 Strings & Atoms are Quantized The possible frequency and energy states of an electron in an atomic orbit or of a wave on a string are quantized. f = v n 2 l En = = nhf, n= 0,1,2,3, h 6.626x10 Js

45 Natural Frequency of Objects & Resonance All objects have a natural frequency of vibration or oscillation. Bells, tuning forks, bridges, swings and atoms all have a natural frequency that is related to their size, shape and composition. A system being driven at its natural frequency will resonate and produce maximum amplitude and energy.

46 When the driving vibration matches the natural frequency of an object, it produces a Sympathetic Vibration - it Resonates!

47 Superposition

48 Interference Phased & Pulsed Waves

49 Interference

50 Interference: Beats beats frequency = difference in frequencies

51 Interference: Beats f = f f f B ave = 2 1 f + f 2 1 2

52 Interference: Beats

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54 Standing Waves on a String f 1 f = 2 f 2 1 f = 3 f 3 1 fn = nf 1

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56 Doppler Effect

57 Doppler Effect

58 Which is traveling at subsonic, sonic, or supersonic speeds? a) Subsonic b) Sonic c) Supersonic

59 Doppler Effect

60 When the duck speed is equal or greater than the speed of waves in water, the waves form a bow wave.

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62 v S v = Mach #

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64 Sonic Boom

65 is a What you Hear The ear converts sound energy to mechanical energy to a nerve impulse which is transmitted to the brain. The Pressure Wave sets the Ear Drum into Vibration.

66 Drum to Stirrup: Simple Machine Amplification Since the pressure wave striking the large area of the eardrum is concentrated into the smaller area of the stirrup, the force of the vibrating stirrup is nearly 15 times larger than that of the eardrum. This feature enhances our ability of hear the faintest of sounds.

67 Resonance of the Cilia Nerves The inner surface of the cochlea is lined with over hair-like cilia connected to nerve cells, each differing in length by minuscule amounts. Each hair cell has a natural sensitivity to a particular frequency of vibration. When the frequency of the sound wave matches the natural frequency of the nerve cell, that nerve cell will resonate with a larger amplitude of vibration which induces the cell to release an electrical impulse along the auditory nerve towards the brain.

68 Sound Waves Transmit Energy Waves transmit energy but there is not net displacement of the medium through which they travel.

69 Cochlear Cilia Nerve Damage Excessive exposure to loud sound can damage your cilia. Normal Ear Damaged Ear

70 The power transmitted by a wave is proportional to the amplitude of the wave.

71 Threshold of hearing :10dB Decibel Index: Whisper: 20db Conversation: 60db Loud Music: 120 db Jet: 140 db Rocket: 250dB

72 OSHA Safety Standards OSHA - Occupational Safety and Health Act - The OSHA criteria document reevaluates and reaffirms the Recommended Exposure Limit (REL) for occupational noise exposure established by the National Institute for Occupational Safety and Health (NIOSH) in The REL is 85 decibels, A-weighted, as an 8-hr time-weighted average (85 dba as an 8-hr TWA). Exposures at or above this level are hazardous.

73 Loudness Perception: Phons Perception of Loudness depends on Frequency & Intensity

74 Sound Frequencies A middle C vibrates 252 times per second. Sonic: 20 Hz 20 khz INFRAsonic: f < 20Hz ULTRAsonic: f > 20kHz

75 Ultrasound:Pulverizing Tumors f I ~23kHz 5 2 ~10 W / m Deep Heat f I ~1MHz 3 2 ~10 W / m

76 Ultrasound Intensity of reflected sound wave (echo) is related to change in density in target. Ultrasound beam: 7MHz 1 mm detail I ~10-2 W

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78 "A Womb With a View" and "Fetal Fotos Peek in the Pod Hi Cost Hi-Definition Ultrasound Are there RISKS? "We do know in animal studies, certain levels of ultrasound can cause damages in growing bones, in developing bones," said Dr. Dan Schultz of the Food and Drug Administration.

79 Animal Perception of Sound domestic cats ,000 Hz domestic dogs 40-46,000 Hz African 16-12,000 Hz elephants ,000 bats Hz rodents ,000 Hz Human: 20-20,00Hz

80 Infrasonic Contact Calls Female African elephants use "contact calls" to communicate with other elephants in their bands (usually a family group). These infrasonic calls, with a frequency of about 21 Hz and a normal duration of 4-5 seconds, carry for long distances (several kilometers), and help elephants to determine the location of other Elephants. Calls vary among individual elephants, so that others respond differently to familiar calls than to unfamiliar calls. Perhaps elephants can recognize the identity of the caller.

81 Infrasonic: < 20Hz Scientists first detected infrasound in 1883, when the eruption of the Krakatoa volcano in Indonesia sent inaudible sound waves careening around the world, affecting barometric readings. The eruption of the Fuego volcano in Guatemala last year generated highamplitude infrasound, mostly below 10 hertz. The pressure readings show that the strength of these sound waves can reach the equivalent of 120 decibels.

82 Echolocation: Sonic Vision Dolphin Vocalization Dolphins produce high frequency (100kHz) clicks that pass through the melon. These sound waves bounce off objects in the water and return to the dolphin in the form of an echo. The brain receives the sound waves in the form of nerve impulses. By this complex system of echolocation, dolphins can determine size, shape, speed, distance, direction, and even some of the internal structure of objects in the water.

83 SOFAR Channel SOund Fixing And Ranging Acoustic Thermometry of Ocean Climate ATOC: 70 Hertz, with a sound pressure level of 195 db Dolphin, pinniped species sensitive to high frequencies (above 10,000 Hz) Baleen whales sensitive to low-frequencies (below 100 Hertz)

84 Low Frequency Active Sonar The LFAS system consists of a 35-ton block of 18 huge underwater speakers and dozens of microphones. The speakers emit a consistent low-frequency tone, between 100 and 500 Hertz, at 240dB, which travels out into the water at a depth of several hundred meters. The low frequency permits the sound to travel tremendous distances, detecting objects many hundreds of miles away by echolocation.

85 Physical Effect on Marine Life At a 1 mile radius from the ship the noise only dissipates to 180 db which causes a bubbling effect in marine mammals' blood stream which creates embolisms. At 100 mile radius from the ship the noise only drops to 160 db which causes shearing of the tissues in the air sack behind whales' and dolphins' brain. This air sack is highly sensitive since it is used in echolocation. This shearing of tissue then causes hemorrhaging in their brains. Fish have little hairs in their ears that transmit sound waves from their ear canals to their central nervous system. The 160 db level shears these hair right off. Granted they grow back in 2 weeks, but they are deaf and are more likely to be picked off by predators and can't find food. Any fish or marine mammals caught in this "death zone" would have to swim 100 miles to escape the noise and pain.

86 Novermber 28, 2004 Sound bombing" of ocean floors to test for oil and gas for National Security? More than 100 whales and dolphins died in two separate beachings in 24 hours on remote Australian islands

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88 Sea Quakes produce powerful pressure waves that rupture the sinuses and middle ear of whales and dolphins.

89 Sound Weapons

90 Atomic Blast Wave

91 Resonance Building and Bridges are made to bend in the wind. To withstand the whirl that s what it takes. All that steel and stone are no match to the wind my friend. What doesn t bend,breaks. What doesn t bend,breaks. -AniDiFranco