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WAVES: Types and Properties

WAVES: Types and Properties. What is a Wave?. A wave is a repeating disturbance or movement that transfers energy through matter or space. The Nature of Waves. Waves transfer energy not matter. Waves can only exist as long as they have energy to carry. How is Energy Carried?.

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WAVES: Types and Properties

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  1. WAVES:Types and Properties

  2. What is a Wave? • A wave is a repeating disturbance or movement that transfers energy through matter or space

  3. The Nature of Waves • Wavestransfer energy not matter. Waves can only exist as long as they have energy to carry.

  4. How is Energy Carried? • Molecules of matter bump each other and pass energy from molecule to molecule.

  5. What are Mechanical Waves? • Mechanical wavesare waves which require a medium. • A medium is a form of matter through which the wave travels (such as water, air, glass, etc.)

  6. Two Shapes of Mechanical Waves: 1. Transverse Waves 2. Compressional Waves

  7. Transverse Waves • In a transverse wavethe matter in the wave moves up and down at a right angle or perpendicularto the direction of the wave • Examples: water waves; seismic waves; electromagnetic waves

  8. Example: Water Wave A water wave travels horizontally as the water moves vertically up and down

  9. Example: Seismic Waves • Like water waves, seismic waves are mechanical, transverse waves • A seismic waveis an energy wave which vibrates through the earth’s crust as the crust bends or breaks. • Some travel through the earth and some travel across the earth’s surface.

  10. Anatomy of a Seismic Wave

  11. Compressional Waves • In a compressional wavethe matter in the wave moves back and forth, parallel to the direction of the wave • Example: sound waves

  12. Example: Sound Waves • Sound wavesare mechanical, compressional waves • There is NO sound in space – because there is no matter for the waves to travel through

  13. What are Electromagnetic Waves? • An electromagnetic waveis a wave that can travel through a medium OR in outer space where there is no matter, or medium. • Electromagnetic waves are also transverse waves • Examples include: • radio waves • microwaves • infrared waves • visible light waves • UV waves • X rays • gamma rays

  14. Wave Properties: Transverse Waves • Crest: top of the wave • Trough:bottom of the wave • Rest Position: half way between the crest and trough

  15. Wave Properties: Transverse Waves • Wavelength is the distance from the top of one crest to the top of the next crest, or from the bottom of one trough to the bottom of the next trough (units = nm, mm, cm, m, km)

  16. Wave Properties: Transverse Waves • Amplitude: height of the wave (from the crest to the rest position; or from the trough to the rest position)

  17. Wave Properties: Amplitude • The lower the amplitude, the less energy the wave carries. • The greater the amplitude, the more energy the wave carries. A) B)

  18. Wave Properties: Compressional Waves • Compression:area squeezed together • Rarefaction: areas spread out • Wavelength: distance from the center of one compression to the center of the next compression (units = nm, mm, cm, m, km)

  19. Wave Properties: Compressional Waves • The amplitude of a compressional wave is determined by the closeness of the compressions. • The closer the compression lines and the farther the rarefaction lines, the greater the amplitude, the greater the energy.

  20. Frequency • The frequency of a wave is the number of wavelengths that pass a given point in 1 second • The unit of frequency is thehertz(Hz). • Larger wavelength = smaller frequency • Smaller wavelength = larger frequency

  21. Color and Pitch • COLOR: the wavelength & frequency of a light wave determines the color of the light. • PITCH: the wavelength & frequency of a sound wave determines the pitch of a sound.

  22. What is the Wavelength?? (nm) 5 10 15 20 25 30 35 40 Wavelength = 25 nm – 5 nm = 20 nm

  23. What is the Wavelength?? 15 20 25 5 10 (nm) Wavelength = 15 nm – 10 nm = 5 nm

  24. Which has a greater Amplitude? A) B)

  25. Which has more energy? A) B)

  26. Which has a greater wavelength? A) B)

  27. Which has a greater frequency? A) B)

  28. What is the Frequency?? (nm) 5 10 15 20 25 30 35 40 • Time = 1 second • Hint: Frequency = wavelengths per second • Answer: 4 Hz

  29. What is the Frequency?? (nm) 5 10 15 20 25 30 35 40 • Time = 2 seconds • Hint: Frequency = wavelengths per second • Answer: 2 Hz

  30. What is the Frequency?? (nm) 5 10 15 20 25 30 35 40 • Time = 0.5 seconds • Hint: Frequency = wavelengths per second • Answer: 8 Hz

  31. Wave Speed • The speed at which a wave travels is its wave speed. • wave speed (v)= wavelength () * frequency (f) • Wavelength is represented by the Greek letter lambda (λ) and frequency is represented by (f) • Sound travels through air at about 340 m/s. Light travels through air at about 300,000,000 m/s.

  32. What is the Wave Speed?? wave speed = wavelength * frequency (m) 5 10 15 20 25 30 35 40 Time = 1 second Frequency = Wavelength = Wave Speed = 4 hz 25 m – 5 m = 20 m 20m * 4hz = 80 m/s

  33. What is the Wave Speed?? wave speed = wavelength * frequency 15 20 25 5 10 (m) Time = 1 second Frequency = Wavelength = Wave Speed = 9 hz 15 m – 10 m = 5 m 5m * 9hz = 45 m/s

  34. Question 1 A rhythmic disturbance that carries energy but not matter is known as a _______. A. electron B. matter C. volcano D. wave

  35. Question 2 The sound of someone clapping their hands is a wave. What kind and shape is it?

  36. Question 3 Why wouldn’t a drum solo sound good in outer space?

  37. Question 4 What shapes of waves are depicted below? A B

  38. Question 5 Label each of the following 4 letters: A. ____________ B. ____________ C. ____________ D. ____________

  39. Question 6 On this compressional wave, what do letters A and B represent? A B

  40. Question 7 The amplitude of a wave is also a measure of the wave’s __________. A. compression B. wavelength C. energy D. motion

  41. Question 8 (nm) 5 10 15 20 25 30 35 40 • What is the frequency of this transverse wave if time = 2 seconds • Hint: Frequency = wavelengths per second

  42. Question 9 If a wave has a frequency of 500 Hz and a wavelength of 90 m, what is its speed? wave speed (v) = wavelength () * frequency (f)

  43. Question 10 wave speed = wavelength * frequency 15 20 25 5 10 (m) • Determine the frequency and wavelength if time is 0.5 seconds • Calculate the wave speed

  44. Answer 1 The correct answer is D. Think of the wave that you send across a bed sheet by shaking one end. Matter does not move across the bed sheet, only energy.

  45. Answer 2 Energy from the clap moves out through the air. It is a mechanical wave because it needs a medium. It is also a compressional wave because of its shape.

  46. Answer 3 You wouldn’t be able to hear a drum in outer space. Where there’s no air, there can be no compression and rarefaction, and thus no sound waves.

  47. Answer 4 A • Compressional • Transverse B

  48. Answer 5 A. Crest B. Trough C. Amplitude D. Rest Position

  49. Answer 6 • Rarefaction • Compression A B

  50. Answer 7 (nm) 5 10 15 20 25 30 35 40 There are 4 wavelengths in 2 seconds which means there are 2 wavelengths in 1 second. Thus the frequency is 2 Hz.

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