The Energy of Waves

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The Energy of Waves
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The Nature of Waves

• Wave
• Medium

• periodic disturbance in a solid, liquid, or gas
• energy being transferred through a medium or
  empty space
• substance through which a wave can travel

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• Mechanical waves
• Electromagnetic waves

• waves that require a medium
• ex. sound waves
• do not require a medium
• travel through emptiness of space and matter

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Types of Waves

• Transverse waves
• 1. Crest
• 2. Trough

• particles move perpendicularly to the direction
  the wave is traveling (up down)
• ex. electromagnetic waves
• highest point on wave
• lowest point on wave

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• Longitudinal Waves
• 1. Compression
• 2. Rarefaction

• particles vibrate parallel to the direction of
  wave motion (back forth)
• ex. sound waves
• particles are pushed together
• particles are spread apart

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• Surface Waves

• Combination of transverse and longitudinal waves
• Wave motion is circular
• Example-Ocean Wave

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Properties of Waves

• Amplitude

• related to height
• max distance from rest position
• waves with large amplitude carry more energy

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• Wavelength
• Frequency

• distance between two crests or two compressions
• shorter wavelengths more energy
• of waves in a given time
• measured in hertz (Hz)
• 1 Hz 1 wave/sec
• high frequency more energy

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• Wave Speed

• speed at which wave travels
• speed wavelength x frequency
• v ? x f
• wavelength and frequency are inversely related

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Wave Interactions

• Reflection
• Echo

• wave bounces back after hitting a barrier
• all waves can reflect
• reflected sound waves

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• Refraction

• bending of a wave as the wave passes from one
  medium to another at an angle
• wave speed and wavelength changes
• ex. rainbows sunlight refracted through water
  droplets

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• Diffraction

• bending of waves around a barrier or through an
  opening
• depends on wavelength and size of barrier
• ex. sound waves can be heard because they have
  longer wavelengths than light waves

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• Interference
• Constructive Interference
• Destructive
• Interference

• two or more waves overlapping
• waves overlap to make larger crests/troughs
  larger amplitude
• crest of one wave overlaps the trough of another
  smaller amplitude
• waves with same crest/trough no wave at all

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• Standing Waves
• Resonance

• pattern of vibration that simulates a wave that
  is standing still
• only looks like it is still
• ex. musician plucks a guitar string
• two objects naturally vibrate at the same
  frequencies
• ex. singing in the shower