Characteristics of Waves

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Characteristics of Waves

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  1. Characteristics of Waves

    Slide 1 - Characteristics of Waves

    • Chapter 20
  2. Waves and Energy

    Slide 2 - Waves and Energy

    • Waves do not carry matter
    • Waves carry energy
    • Scientific definition: a traveling disturbance that carries energy from one place to another
  3. Where do waves get energy?

    Slide 3 - Where do waves get energy?

    • Waves get their energy from a vibration
    • An object that is vibrating is moving
    • A moving object has energy
  4. What do waves travel through?

    Slide 4 - What do waves travel through?

    • Medium is the matter or substance a wave travels through
    • Waves that require a medium are mechanical waves
    • Waves that do not require a medium to travel through are called electromagnetic, they travel through a vacuum
  5. Characteristics of Waves

    Slide 5 - Characteristics of Waves

    • All waves have amplitude, wavelength, and frequency
    • Parts of a wave: crest and trough
  6. Amplitude

    Slide 6 - Amplitude

    • When a wave moves from its resting place to the crest it is measuring its amplitude
    • The amplitude of a wave indicates the amount of energy carried by the wave
  7. Wavelength

    Slide 7 - Wavelength

    • The distance between two crests or two troughs
    • Symbol is λ Greek letter lambda
  8. Frequency

    Slide 8 - Frequency

    • The number of complete waves per unit cycle
    • Unit used is called Hertz for Heinrich Hertz who studied waves
    • 1 hz = 1 wave/sec
  9. Transverse Waves

    Slide 9 - Transverse Waves

    • A wave in which the motion of the medium is at right angles to the direction of the wave
  10. Longitudinal Waves

    Slide 10 - Longitudinal Waves

    • A wave that consists of a series of compressions and rarefactions
    • The motion of the medium is parallel to the direction of the wave
  11. Combinations of Waves

    Slide 12 - Combinations of Waves

    • Surface wave is the combination of both transverse and longitudinal waves
  12. Speed of Waves

    Slide 13 - Speed of Waves

    • The speed of a wave is determined by the number of waves passing a point in a certain amount of time (frequency) and the length of the wave (λ)
    • Speed = frequency * wavelength
    • A wave with a frequency of 4 hertz and a λ of 2 meters has a speed of 8 m/sec
    • The speed of a wave depend upon the medium through which it travels and it is always constant
  13. Interactions of Waves

    Slide 14 - Interactions of Waves

    • The four basic wave interactions are reflection, refraction, diffraction, and interference
  14. Reflection

    Slide 15 - Reflection

    • Is the bouncing back of a wave after it hits a boundary
    • Law of Reflection states that the angle of incidence is equal to the angle of reflection
  15. Refraction

    Slide 16 - Refraction

    • The bending of waves due to the change in speed, this is due to the speed at which waves travel in different mediums
  16. Diffraction

    Slide 17 - Diffraction

    • The bending of waves around the edge of an obstacle
    • The amount of diffraction depends on the wavelength and the size of the obstacle
  17. Interference

    Slide 18 - Interference

    • When 2 or more waves arrive at the same place at the same time they react in a process called interference. The waves combine to form a single wave
  18. Constructive Interference

    Slide 19 - Constructive Interference

    • If the waves combine in a way to make that the disturbance that results is greater than either wave alone
  19. Destructive Interference

    Slide 20 - Destructive Interference

    • If the waves combine in such a way that the disturbance that results is less than either wave alone
  20. Standing Waves

    Slide 21 - Standing Waves

    • A wave that does not appear to be moving
    • The points on a standing wave where destructive interference results in no energy displacement are called nodes
    • The points at which constructive interference causes maximum energy are called antinodes
  21. Resonance

    Slide 23 - Resonance

    • The frequency at which a standing wave occurs is called the natural frequency or resonant frequency.
    • In real life, waves usually give a mishmash of constructive and destructive interference and quickly die out. However, at certain wavelengths standing waves form, resulting in resonance. These are waves that bounce back into themselves in a strengthening way, reaching maximum amplitude.
  22. Sound

    Slide 24 - Sound

    • Chapter 21
  23. How Sounds are Made

    Slide 25 - How Sounds are Made

    • Sounds are vibrations that travel in longitudinal waves
    • A vibration is the complete back and forth motion of an object
    • At the crest of each wave is a compression of the molecules of the medium
    • At the trough is a rarefaction of the molecules of the medium
  24. Sound and Media

    Slide 26 - Sound and Media

    • Medium is the substance that the sound wave travels through
    • Fastest in solids, then liquids, then gases.
    • Why?
    • Space is a vacuum, with no matter to carry the sound wave, so no sound is heard from space.
  25. Slide 27

    • Threshold of Hearing
    • 0dB Normal Breathing
    • 10dB Rustling Leaves
    • 20dB
    • 30dB Library
    • 40dB
    • 50dB Normal Conversation
    • 60dB
    • 70dB Noisy Office with machines
    • 80dB Heavy Traffic
    • 90dB
    • 100dB Construction Noise (up close)
    • 110dB
    • Threshold of Pain
    • 120dB Rock Concert
    • 130dB
    • 140dB Jet Takeoff (from runway)
    • 150dB
  26. Human Hearing

    Slide 28 - Human Hearing

    • Infrasonic – sounds 0-20 hz to low for humans to hear
    • Ultrasonic - sounds greater than 20,000 hz to high for humans to hear
    • Most humans can hear 20-20,000 hz most of their lives.
  27. Hearing Loss and Deafness

    Slide 29 - Hearing Loss and Deafness

    • The most common type of hearing loss is called tinnitus, caused by exposure to loud sounds or music
    • How to prevent it? Turn your I-pods down!!!!!!
    • Protect your hearing by wearing ear protectors if you know you are going to be exposed to loud noise.
  28. Speed of Sound

    Slide 31 - Speed of Sound

    • The speed of sound is determined by the temperature, elasticity, and density of the medium through which the sound travels
  29. Temperature

    Slide 32 - Temperature

    • Sound travels faster at higher temperatures and slower at lower temperatures due to the molecules of the medium
    • Air at 0° 331 m/sec
    • Air at 25° 346 m/sec
  30. Elasticity and Density

    Slide 33 - Elasticity and Density

    • Solids are more elastic than either liquids or gases, the medium returns to its original position ex. Running on pavement or sand
    • Sound travels best in solids, then liquids, and worst in gases because the molecules are closer together in solids
  31. Frequency and Pitch

    Slide 34 - Frequency and Pitch

    • The description of a sound as either high or low is its pitch
    • The pitch depends on the frequency of a sound
    • High frequency=high pitch low frequency=low pitch
  32. Pitch

    Slide 35 - Pitch

  33. Doppler Effect

    Slide 36 - Doppler Effect

    • The change in pitch due to the movement between the sound and the receiver
    • Coming toward the receiver the sound waves are pushed together
    • Moving away the sound waves have more space between them
  34. Intensity and Loudness

    Slide 37 - Intensity and Loudness

    • Intensity determines the loudness of a sound
    • Intensity is the amount of energy carried in a wave in a certain amount of time
    • The larger the amplitude the greater the intensity of a wave
  35. Reflection of Sound Waves

    Slide 38 - Reflection of Sound Waves

    • Reflection of sound waves is called an echo
    • Echolocation
  36. Sonar

    Slide 39 - Sonar

    • High frequency ultra-sonic waves are used in a system called Sound Navigation And Ranging or sonar
  37. Ultrasounds

    Slide 40 - Ultrasounds

    • Ultrasonic waves are directed into a body and the resulting picture can be seen from the deflected waves
    • http://www.youtube.com/watch?v=opCo2xZ9W8I&feature=related
  38. Combining Sounds

    Slide 41 - Combining Sounds

    • When sound waves combine in such a way that the resulting disturbance is greater then either wave alone, constructive interference occurs
    • When constructive interference occurs the resulting sound gets louder
    • Acoustics is the science of sound, acoustic engineers design auditoriums to eliminate interference problems
  39. Destructive interference results when two sound waves combine and the resulting sound is less that the two original sounds

    Slide 42 - Destructive interference results when two sound waves combine and the resulting sound is less that the two original sounds

    • The sound gets softer
  40. Slide 43

    • Constructive Destructive
    • Interference Interference
  41. Sonic Boom

    Slide 44 - Sonic Boom