yr9 - waves introduction

Dr Pusey

www.puseyscience.com

Waves are periodic oscillations that transfer energy from one point to another.

The oscillations are “disturbances” or “deviations from the normal location” in matter

We generally think of this when we think of waves:

Transverse – Wave oscillation is perpendicular (up & down) to wave velocity direction.

Longitudinal – Wave oscillation is in the same direction (along the wave) to wave velocity direction

Wave Motion

Heinemann Physics 3A/3B – pg 186 - 187

Transverse VS Longitudinal

http://www.acs.psu.edu/drussell/Demos/waves/wavemotion.html

TRANSVERSE: Particles oscillate perpendicular to wave motion (up and down):

LONGITUDINAL: Particles oscillate parallel to wave motion (back and forth)

Fun Facts Strings, Ocean Waves, Sound, etc

The frequency of mechanical waves determines if we can hear them or not (audible spectrum).

In fluids (air and water), sound waves are almost exclusively longitudinal.

A vibrating guitar string is a transversewave

Sound travels from the guitar string to your ear in a longitudinal wave

Fill in the blanks: Listening to mad tunes on Triple J:

Sick Tunes

Radio Station

Radio

Listener

Longitudinal

Transverse

Longitudinal

Fun Facts - Electromagnetic WavesLight, Radio Waves, X-rays, all oscillations

of the electromagnetic field.

The frequency of electromagnetic waves determines if we can see them or not. (visible spectrum)

You will learn more about light waves in particular in year 12

Term Definition SI units

Frequency ( f ) Number of fluctuations/ oscillations/cycles per second

Hz or s-1

Wavelength ( λ ) The distance between each successive wave

m

Period ( T ) The time between each successive wave

s

Amplitude ( A ) The deviation from the mean, of whatever is being studied. (e.g. displacement, pressure, etc)

Whatever the units of what is changing over time (e.g. m, Pa, etc)

Ocean wave as measured by eye

This is a measurement of Amplitude VS Distance

wavelength

Amplitude

Crest

Trough

Pictures of Waves Both Transverse and Longitudinal waves are

represented the same way on a graph.

Heinemann Physics 3A/3B – pg 189

Your Turn

What is the amplitude and wavelength of this wave?

Your Turn

What is the amplitude and wavelength of this wave?

Amplitude = 4 cmWavelength = 20 cm

λ

A