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WAVES. Simple Harmonic Motion (SHM). - sometimes called oscillatory motion the back and forth vibratory motion of a swinging pendulum - sine curve - the shape of the line a swinging pendulum makes over a constantly moving surface. What is a Wave?.

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Simple harmonic motion shm
Simple Harmonic Motion (SHM)

- sometimes called oscillatory motion

  • the back and forth vibratory motion of a swinging pendulum

    - sine curve - the shape of the line a swinging pendulum makes over a constantly moving surface


What is a wave
What is a Wave?

A wave is a disturbance that carries energy through matter or space.

Medium - the matter that a wave travels through. Examples: water, air, steel, the Earth


Types of waves
Types of Waves

Mechanical Waves - waves that require a medium.

All waves, except light, are mechanical waves.

Electromagnetic Waves - waves that consist of changing electric and magnetic fields in space.


Wave characteristics
Wave Characteristics

Crests - the high points of a wave

Troughs - the low points of a wave

Amplitude - the distance from the midpoint to the crest (or trough) of a wave

Wavelength - the distance between successive identical parts of a wave (crest to crest or trough to trough)



Wave characteristics1
Wave Characteristics

Period - the time it takes for one complete wave

- time ÷ # of waves

- measured in time units

Frequency - the number of waves that pass a point in a given amount of time

- # of waves ÷ time (usually seconds)

- measured in Hertz (Hz)


Frequency and period
Frequency and Period

Period = 1

frequency

Frequency = 1

period


Problems
Problems

  • What is the frequency, in hertz, that corresponds to each of the following periods?

    a. 0.10 s

    b. 5 s

    c. 1/60 s

    d. 24 h


Problems1
Problems

2. What is the period, in seconds, that corresponds to each of the following frequencies?

a. 10 Hz

b. 0.2 Hz

c. 60 Hz

d. 0.8 Hz


Problems2
Problems

3. A metronome is set so that it makes ten complete vibrations in 12 seconds. Find the frequency of the metronome.


Wave speed
Wave Speed

In linear motion:

speed = distance (m/s)

time

In wave motion:

speed = wavelength x frequency

v =  ƒ (m · 1/s = m/s)


Problems3
Problems

A wave with wavelength 10 m passes a pier with a frequency of 2 Hz. What is the speed of the wave?


Problems4
Problems

A wave with wavelength 10 m passes a pier with a frequency of 2 Hz. What is the speed of the wave?

  • = 10 m

  • = 2 Hz

    v = ?


Problems5
Problems

A wave with wavelength 10 m passes a pier with a frequency of 2 Hz. What is the speed of the wave?

  • = 10 m v = 

  • = 2 Hz v = (10m)(2Hz)

    v = ? v = 20 m/s


Practice
Practice

If a water wave vibrates up and down two times each second and the distance between wave crests is 1.5 m, what is the frequency of the wave?

What is its wavelength?

What is its speed?


Practice1
Practice

If a water wave vibrates up and down two times each second and the distance between wave crests is 1.5 m, what is the frequency of the wave?

 = 2 Hz

What is its wavelength?

 = 1.5 m

What is its speed? v = 3 m/s


Practice2
Practice

While sitting on a pier, Carlos notices that incoming waves are 2.0 m between crests. If the waves lap against the pier every 0.5 s, find

  • the frequency.

    b) the speed of the wave.


Practice3
Practice

While sitting on a pier, Carlos notices that incoming waves are 2.0 m between crests. If the waves lap against the pier every 0.5 s, find

  • the frequency.

     = 2 Hz

    b) the speed of the wave.

    v = 4 m/s


Kinds of waves
Kinds of Waves

Transverse Waves - the motion of the medium is at right angles to the direction in which the wave travels.

(Look like a sine curve.)

Example: water waves, light waves


Kinds of waves1
Kinds of Waves

Longitudinal Waves - the particles move along the direction of the wave (rather than at right angles to it).

Example: sound waves


Standing waves
Standing Waves

Standing waves occur when the original wave and the reflected wave combine to form a wave where parts of the medium do not move.



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