Earthquakes and Waves

Oscillation

A motion that regularly repeats itself back and fourth

Characteristics of an oscillation

Frequency, Amplitude, Displacement, Damping

Frequency

rate of an oscillation

Frequency (unit)

Hertz (Hz)

Amplitude

maximum displacement from equilibrium position

Damping

Oscillation that fades away with time

(Time period / Frequency) equation

T=1/f (time period = 1/frequency)

Time period (symbol)

T

Frequency (symbol)

f

Amplitude (symbol)

A

Natural frequency

The frequency at which an object vibrates naturally when disturbed

Resonance

When an external force forces another system to vibrate with a greater amplitude

Example of resonance

guitar, swing, singer breaking glass

Characteristics of waves

Wavelength, Frequency, Speed, Amplitude, Phase

Wavelength (symbol)

λ (lambda)

Wavelength

distance between crests or troughs

highest point of a wave

crest

lowest point of a wave

trough

Frequency (symbol)

f

Speed (symbol)

v

Speed

the distance a wave travels in a given amount of time

Phase

Points on a wave with the same speed and direction are in phase

The wave equation

v=f λ (speed = frequency x wavelength)

Types of waves

Longitudinal waves, Transverse waves

P waves

Longitudinal waves

S waves

Transverse waves

Longitudinal waves include…

compression and refraction

In longitudinal waves the medium …

moves parallel to the direction of the wave

In transverse waves the medium …

moves perpendicular to direction of the wave

The motion in transverse waves is …

up and down

High density medium … speed of wave

increases

Low density medium … speed of wave

decreases

high temperature … speed of wave

high

low temperature … speed of wave

low

speed of sound in air equation

2d/t (distance travelled/time taken)

Echolocation

determines location of objects using reflected sound waves