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Waves

Textbook pages 92-99. Perception of Light & Sound. Waves. What is a WAVE?. A disturbance that travels through a medium. What is a WAVE?. A disturbance that travels through a medium Medium: a substance that carries the disturbance from one location to another. What is a WAVE?.

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Waves

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  1. Textbook pages 92-99 Perception of Light & Sound Waves

  2. What is a WAVE? • A disturbance that travels through a medium

  3. What is a WAVE? • A disturbance that travels through a medium • Medium: a substance that carries the disturbance from one location to another

  4. What is a WAVE? • A disturbance that travels through a medium • Medium: a substance that carries the disturbance from one location to another • How? The particles of the medium interact with particles next to them allowing the disturbance to travel • Examples of a medium • Water • Air • Ground

  5. What is a WAVE? • Transports energy from one place to another

  6. What is a WAVE? • Transports energy from one place to another

  7. What is a WAVE? • Transports energy from one place to another • Particles of the medium are only temporarily displaced from the rest position

  8. What is a WAVE? • Transports energy from one place to another • Particles of the medium are only temporarily displaced from the rest position • Does not transport matter

  9. Wave Characteristics • Propagation • Amplitude • Wavelength • Frequency

  10. Propagation • Waves are distinguished by the way they propagate through a medium

  11. Propagation • Transverse Waves • Propagates perpendicular to the motion of the medium Motion of the Medium Wave Motion

  12. Propagation • Transverse Waves CREST Equilibrium TROUGH

  13. Propagation • Longitudinal Waves • Propagates parallel to the motion of the medium Wave Motion Motion of the Medium

  14. Propagation • Longitudinal Waves • Propagates parallel to the motion of the medium Wave Motion Motion of the Medium

  15. Propagation • Longitudinal Waves • Propagates parallel to the motion of the medium Wave Motion Motion of the Medium

  16. Propagation • Longitudinal Waves • Propagates parallel to the motion of the medium Region of Compression Region of Rarefaction

  17. Amplitude (A) • Related to the amount of energy transferred by a wave

  18. Amplitude (A) • Transverse Waves • Maximum distance travelled by a particle in the medium compared to its equilibrium position Equilibrium

  19. Amplitude (A) • Transverse Waves • Depends on energy transmitted by the wave

  20. Amplitude (A) Region of low-density compression • Longitudinal Waves • How tightly the medium is pushed together at the compressions Region of High-density compression

  21. Amplitude (A) • Longitudinal Waves • Depends on the density of compression

  22. Wavelength () • Length of a wave’s complete cycle • Transverse Waves  Cycle

  23. Wavelength () • Length of a wave’s complete cycle • Longitudinal Waves  Cycle

  24. Frequency (f) • Number of cycles per unit of time • Measured in Hertz (Hz) – the number of cycles per second • 1 Hz = completes one full cycle in one second Cycle Cycle

  25. Speed at which a Wave Travels • Speed of a wave depends on • Medium it travels in • Temperature

  26. Determine the speed at which a Wave Travels • Speed = frequency x wavelength

  27. Determine the speed at which a Wave Travels • Speed = frequency x wavelength • v = f x  • v = speed (m/s) • f = frequency (Hz) •  = wavelength (m)

  28. Determine the speed at which a Wave Travels • What is the speed of a sound wave that has a wavelength of 2.00m and a frequency of 170.5Hz? G R A S P

  29. Determine the speed at which a Wave Travels • What is the speed of a sound wave that has a wavelength of 2.00m and a frequency of 170.5Hz? G R A f = 170.5Hz = 2.00m S P

  30. Determine the speed at which a Wave Travels • What is the speed of a sound wave that has a wavelength of 2.00m and a frequency of 170.5Hz? G R A f = 170.5Hz = 2.00m S P v = ?

  31. Determine the speed at which a Wave Travels • What is the speed of a sound wave that has a wavelength of 2.00m and a frequency of 170.5Hz? G R A f = 170.5Hz = 2.00m S P v = ? v = f x 

  32. Determine the speed at which a Wave Travels • What is the speed of a sound wave that has a wavelength of 2.00m and a frequency of 170.5Hz? G R A f = 170.5Hz = 2.00m v = (170.5Hz)(2.00m) v = 341 m/s S P v = ? v = f x 

  33. Determine the speed at which a Wave Travels • What is the speed of a sound wave that has a wavelength of 2.00m and a frequency of 170.5Hz? G R A f = 170.5Hz = 2.00m v = (170.5Hz)(2.00m) v = 341 m/s S P v = ? The speed of the sound wave is 341 m/s v = f x 

  34. Types of Waves • Mechanical Waves • Electromagnetic Waves

  35. Mechanical Waves • Can only propagate in a medium

  36. Mechanical Waves • Can only propagate in a medium • How? A disturbance changes the physical shape of the medium and passed onto neighbouring particles

  37. Mechanical Waves • Can only propagate in a medium • How? A disturbance changes the physical shape of the medium and passed onto neighbouring particles • Examples: water waves, sound waves, seismic waves

  38. Electromagnetic Waves • Can propagate in a medium and a vacuum

  39. Electromagnetic Waves • Can propagate in a medium and a vacuum • Carry Radiant Energy

  40. Electromagnetic Waves • Can propagate in a medium and a vacuum • Carry Radiant Energy • Examples: light waves in space

  41. Electromagnetic Spectrum • Categories of electromagnetic waves • Classified by frequency and wavelength

  42. Electromagnetic Spectrum Long Short High Low

  43. Electromagnetic Spectrum • Radio Waves • Smallest frequency • Invisible & transport little energy • Example: Radio, Television, Microwaves, Cellphones

  44. Electromagnetic Spectrum • Infrared • Invisible, but feel the warmth emitted • Example: Night vision goggles, short-distance communication (wireless keyboards, remote controls, etc.)

  45. Electromagnetic Spectrum • Visible Light • Only electromagnetic waves that can be seen by humans • Together, colours make up white light • Example: Photography, movies, computer screens

  46. Electromagnetic Spectrum • Ultraviolet Rays (UV) • Invisible to humans • Greater frequency, transport more energy • Responsible for suntans, but can cause cancer • Example: sterilization of surgical instruments, treatments

  47. Electromagnetic Spectrum • X-Rays • High frequency • Able to travel through media opaque in visible light • Example: baggage inspection, radiography

  48. Electromagnetic Spectrum • Gamma Rays • Highest frequency and transports the highest energy • Travel easily through matter • Can cause burns, cancer, and genetic mutations • Example: cancer treatment, food preservation

  49. Homework • Read Textbook pages 92-99 • Do Workbook pages 49-52

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