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Waves

Unit 9 - Light & Sound

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Lesson 1: Questions

  • What are the similarities and differences between transverse and longitudinal waves?

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  • How is a wave’s amplitude related to its energy?

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  • How are frequency and wavelength related?

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Vocabulary

Define the following vocabulary words:

  • Wave
  • Medium
  • Transverse Wave
  • Crest
  • Trough
  • Longitudinal/Compressional Wave
  • Compression
  • Rarefaction
  • Amplitude
  • Wavelength
  • Frequency

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Waves

Wave - a repeating motion that carries energy through space or a medium

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Waves

Medium - a material through which waves transfer energy

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Waves

Medium - a material through which waves transfer energy

  • Can be a solid, liquid, gas, or combination
  • The medium does not travel with the wave

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  • Not all waves need a medium!
    • Sound waves need a medium
    • Light waves do not need a medium

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Types of Waves

Transverse Wave - the medium moves at a right angle to the direction the wave is traveling

  • Ex: Light waves

Medium Direction

Direction of Energy

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Structure of a Transverse Wave

Crest - the highest point of a wave

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Trough - the lowest point of a wave

Rest Position

Crest

Crest

Crest

Trough

Trough

Trough

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Types of Waves

Longitudinal/Compressional Wave - the medium vibrates in the same direction as the wave is traveling

  • Ex. Sound waves

Direction of Energy

Medium Direction

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Types of Waves

Wave - a repeating motion that carries energy through space or a medium

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Structure of a Compressional Wave

Compression - crowded area of the wave

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Rarefaction - less crowded area of the wave

Compression

Rarefaction

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Amplitude

Amplitude - the distance from the rest position of the wave to a crest or trough

Amplitude

Amplitude

Rest Position

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Amplitude

Amplitude - the distance from the rest position of the wave to a crest or trough

  • Amplitude describes the energy or intensity of a wave

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HIGH amplitude = HIGH energy light wave = BRIGHT

LOW amplitude = LOW energy light wave = DIM

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Amplitude

Amplitude - the distance from the rest position of the wave to a crest or trough

  • Amplitude describes the energy or intensity of a wave

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HIGH amplitude = HIGH energy sound wave = LOUD

LOW amplitude = LOW energy sound wave = SOFT

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Wavelength

Wavelength (λ) - the distance between two identical parts of a wave

  • Measured crest to crest
  • Measured trough to trough

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Wavelength

Wavelength

Crest

Crest

Trough

Trough

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Wavelength

Wavelength (λ) - the distance between two identical parts of a wave

  • Measured compression to compression
  • Measured rarefaction to rarefaction

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Wavelength

Wavelength

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Frequency

Frequency - the number of waves passing a point per second

  • Units: Hertz (Hz)
  • Describes the color/type of light

HIGH frequency = Ex. UV Light Waves

LOW frequency = Ex. Radio Waves

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Frequency

Frequency - the number of waves (# of vibrations) passing a point per second

  • Units: Hertz (Hz)
  • Describes the pitch of a sound

HIGH frequency = HIGH PITCH sound

LOW frequency = LOW PITCH sound

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Frequency

LIGHT SOUND

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High frequency = Short wavelength

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Low frequency = Long wavelength

Wavelength

Wavelength

Wavelength

Wavelength