QOTD

1. QOTD 1: What is a Transverse wave? A longitudinal wave? 2: Which one needs a medium?

2. ANSWERS TO QOTD… 11/30/2009 • 1:TRANSVERSE: vibrates perpendicularto the direction in which the wave travels • LONGITUDINAL: vibrates parallelto the direction in which the wave travels • 2: BOTH • Only ELECTROMAGNETIC WAVES do not require a medium!!

3. Light, SOUND, and color Chapter 12 Notes

4. Remember… • TYPES OF WAVES • Transverse Waves • Longitudinal Waves • Electromagnetic Waves (or Light Waves)

5. Transverse wave, matter vibrates up and down (perpendicular) to the direction in which the wave travels. A transverse wave can carry energy without using matter.

6. Compressional (longitudinal or sound) wave particles are displaced back and forth parallel to the direction of the wave; it requires a medium to travel. hand drawn way

7. At a constant speed, if frequency increasesthewavelength decreases, or when frequencydecreases the wavelength increases. V = F   Click here to go to interactive website on frequency and wavelength

8. Speed of Sound • The Speed of sound depends on the medium. • Sound waves travel faster through liquids and solids than through gases. • In a liquid or solid, the particles are much closer together than in a gas, so the vibrations are transferred more rapidly from one particle to the next.

9. Speed of Sound • Some solids, such as rubber, dampen vibrations so that sound travels very slowly. • Materials like rubber can be used for soundproofing.

10. Speed of sound… The speed of sound can be used to estimate distances. Sound travels at 343 m/s at standard temperature and pressure. Sound travels best in SOLIDS.Sounds can NOT travel at all in space (or in any vacuum)

11. Speed of Sound in a Variety of Mediums Medium Temp (oC) Velocity (m/s) Gases air20 343 Liquids water201482 Solids lead1960 copper5010 glass5640 steel 5960

12. 5 Summary ideas about sound travels: 1. Sound travels in a compressional wave. 2. A higher frequency means a higher pitch. 3. Sound travels fastest through solids 4. Soundcannot travel without a medium. 5. Soundcannot travel in space, or any vacuum.

13. LOUDNESS • Loudness of a sound depends partly on the energy contained in the sound waves. • Energy of mechanical (or a sound) wave is determined by its amplitude. • Therefore, the greater the amplitude of the sound wave, the greater the sound.

14. LOUDNESS • Loudness also depends on your distance from the source of sound waves. • The INTENSITY of a sound describes its loudness at a particular distance from the source of the sound.

15. Intensity • The relative intensity of sound is found by comparing the intensity of a sound with the intensity of the quietest sound a person can hear, the threshold of hearing. • The relative intensity is measured in units called decibels, dB. • Extensive exposure to sounds above 120 dB can cause permanent deafness.

16. intensity Intensity depends on the strength of the compressions. (VOLUME = intensity)

17. PITCH • The pitch of a sound is determined by the frequency of the wave, which is measured in Hertz. • The greater the frequency, the higher the pitch. (Ex. The squeak of a shoe on the floor has a high pitch. The drone of a semi truck is a low pitch)

18. PITCH • Wavelength vs. Frequency (Pitch) of SOUNDS: Squeak = High Pitch = High Frequency = small wavelength. Growl= low pitch= low frequency =Large Wavelength

19. Human Ear and Sound... The range of human hearing is between 20 Hz and 20,000 Hz. Most humans cannot hear frequencies outside this range.

20. Ultrasonic vs. Infrasonic • Ultrasonic sounds have frequencies above20,000 Hz. (used by dolphins and birds) • Infrasonic sounds have frequencies below20 Hz. (used by elephants and whales)

21. Echo..echo..echo..o..o…o…o…o… Echo - a sound wave that reflects off a surface. If you direct a loud sound at a hard surface, the sound will bounce back to you. Reduce echos by using soft surfaces. (curtains, carpet, padded walls and seats)

22. Echolocation is a way that sound is used to measure distances using echoes.Applications of echolocation include: submarine, ultrasound or sonagrams, and radar. Echolocation is used by dolphins, insects, bats and birds.

23. Echo Example Problems C. How far is a dolphin from his pod if the speed of his sonar signal travels at 1482 m/s and it takes 20s for the sound to go from him, to the pod and back?

24. Echo Example Problems pod dolphin C.How far is a dolphin from his podif the speed of his sonar signal travels at 1482 m/s and it takes 20 s for the sound to gofrom him, to the podand back?

25. dolphin pod Echo Example Problems C. How far is a dolphin from his pod if the speed of his sonar signal travels at 1482 m/s and it takes 20 s for the sound to go from him, to the podand back? given formula sub answer V = D T

26. dolphin pod Echo Example Problems C. How far is a dolphin from his pod if the speed of his sonar signal travels at 1482 m/s and it takes 5s for the sound to go from him, to the podand back? given formula sub answer V= 1482 m/s D = D T =20 2=10 s V = D T 1482 = D 10

27. dolphin pod Echo Example Problems C. How far is a dolphin from his pod if the speed of his sonar signal travels at 1482 m/s and it takes 5 s for the sound to go from him, to the podand back? given formula sub answer 1482 = D 10 V= 1482 m/s D = D T =20  2=10 V = D T What next ?

28. dolphin pod Echo Example Problems C. How far is a dolphin from his pod if the speed of his sonar signal travels at 1482 m/s and it takes 20s for the sound to go from him, to the podand back? given formula sub answer 1482 = D 10 V= 1482 m/s D = D T =20  2=10 V = D T 1482 x 10 =

29. dolphin pod Echo Example Problems C. How far is a dolphin from his pod if the speed of his sonar signal travels at 1482 m/s and it takes 20s for the sound to go from him, to the podand back? given formula sub answer 1482 = D 10 V= 1482 m/s D = D T =20  2=10 V = D T 14,820 m 1482 x 10 =

30. Doppler Effect (REVIEW) • As the listener moves closer to the source of the sound, the waves have an increased frequency, resulting in a higher pitch. • As the listener moves farther away from the source of the sound, the frequency is reduced which results in a lower pitch.

31. HARMONICS • Harmonics give every instrument a unique sound. • If you play the same note on a tuning fork and a clarinet, the two notes will sound different from each other. • A clarinet will produce sounds at several different pitches, while a tuning fork produces a pure tone of only one pitch.

32. harmonics • A tuning fork vibrates only at its fundamental frequency. • The air column in the clarinet vibrates at its fundamental frequency and at certain whole-number multiples of that frequency called HARMONICS.

33. resonance Resonance is the tendency of an object to vibrate at the same frequency as another vibrating source.Ex. Speakers in a car can get so loud, the car dash vibrates too. Ex. Hit a tuning fork and rest it on a table. Rest it on a test tube in a rack. --Instruments use resonance to amyplify sound. (ex-guitar…pluck a string and it as well as the body will vibrate)

34. Hearing and the ear • SOUND WAVES are transmitted as vibrations through the ear. (see fig 12-7) • Vibrations pass through 3 regions in ear. • OUTER  MIDDLE  INNER Middle ear Inner ear Outer ear

35. Hearing and the ear Waves enter the outer ear, and travel through the ear canal until they strike the eardrum Vibrating air causes the eardrum to vibrate These vibrations enter the middle ear, containing the 3 smallest bones in the body The small bones transfer the vibration to the side of the cochlea The fluid in the spiral of the cochlea vibrates and creates waves that travel up the spiral Nerves at different locations along the spiral will respond todifferent frequencies The nerve cells convert the vibrations in the liquid to electric impulses and send them to the brain The brain interprets the impulses as a sound

36. 15 min break from notes… • Take 15 minutes to work SILENTLY on the worksheet you picked up when you came into class. You will need to open your book to page 396 in order to complete the assignment.

37. Regions of the EAR (pg 396) • Ear Pina (tiny hairs) • Hammer • Anvil • Eardrum • Stirrup • Ear Canal • Vestibular Organs • Auditory nerve • Cochlea

38. Ultrasound and sonar • SONAR Stands for Sound Navigation and Ranging.

39. ULTRASOUND AND SONAR • SONAR • Sonar is used for underwater location. • A sonar systemdetermines distance by measuring the time it takes for sound waves to be reflected back from a surface. • Calculated using the equation: d = vt

40. Ultrasound and sonar • ULTRASOUND • Ultrasound imaging used in medicine. • The echoes of very high frequency ultrasound waves, are used to produce computerized images called sonograms. • Can safely view organs without surgery and unborn fetuses.

41. HOMEWORK… • PAGE 398 Section 12.1 Review 1-2 and 4-6 And Complete all ch 12 vocab!