Waves

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Waves

• conceptual physics level 2

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What is harmonic motion?

• Harmonic motion is any motion that repeats
  itself over and over again.
• Harmonic motion is different than linear motion
  because harmonic motion is a repetitive motion.
• So anything that repeats it motion has harmonic
  motion
• Can you think of examples of this?
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•  These systems of harmonic motion are known as
  oscillators. 
• An oscillation/vibration is a motion that repeats
  itself.

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How do we describe harmonic motion?

• cycle
• one complete back and forth motion (pendulum)
• period
• the time it takes for one cycle
• measured in seconds (s)
• frequency
• the number of cycles per second 
• measured in hertz (Hz)
• amplitude
• the distance from the equilibrium point

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Pendulums

• The period of a pendulum is only affected by the
  length of the pendulum.
• The period is not affected by the angle of the
  pendulum or by the mass of the pendulum.
• Period and frequency are inversely related, so
• of 15Hz?

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Period vs Frequency

• Period  T 1/f 
• and
• Frequency   f 1/T
• Practice problems
• What is the frequency of a pendulum that has a
  period of 2.5s?
• What is the period of a pendulum that has a
  frequency of 0.25Hz?

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Anatomy of a wave

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Waves

• A wave is a vibration that transfers energy (not
  matter) over a distance.
• There are two general types of waves
• mechanical waves
• sound
• water
• etc
• electromagnetic waves
• Visible light
• radio
• x-rays

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Mechanical Waves

• Mechanical waves, unlike electromagnetic waves,
  need a medium to travel through. 
• This means the need some type of matter to travel
  through, solid, liquid, or gas.
• There are two types of mechanical waves
• Transverse
• The wave moves up and down.
• Longitudinal
• The wave moves in one path (also known as a
  compression wave).

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More about longitudinal waves
The reason that a longitudinal wave is called a
compression wave is that the vibration occurs in
a series of areas of compression and then areas
of rarefaction.

• Compression Where particles are closer together
  and bunch up. (Literally, the particles are
  compressed)
• Rarefaction Where particles are further apart
  and are fewer in number. (Literally, the
  particles are becoming rarer)

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Comparing Longitudinal and Transverse