Waves

Opening scene from:

Billabong Odyssey

Wave Properties

• Wave – A rhythmic disturbance that carries energy through matter or space.

• Pulse – Single ‘bump’ / disturbance that travels through medium.

• Medium – matter (or lack thereof) through which waves travel.

Transverse Waves• Wave that vibrates medium perpendicular to

direction of wave motion.

Longitudinal Wave• Wave that vibrates medium parallel to

direction of wave motion.

Sound

Molecules resonating in a closed pipe

Water waves are a combination of transverse and longitudinal.

Combination Waves

Great Men Who Lived Among Waves

Duke Kahanamoku

Eddie Aikau

Measuring a Wave

• Amplitude

• Period

• Frequency

• Wavelength

• Velocity

Waves at BoundariesIncident Wave

Reflected Wave Transmitted Wave

Wave Motion

Wave MotionWave Motion

Before

After

Waves at Boundaries• From Low Density to High Density

Reflected ‘Inverted’, Transmitted ‘Upright’

Animations courtesy of Dr. Dan Russell, Kettering University

Waves at Boundaries• From High Density to Low Density

Reflected ‘Upright’, Transmitted ‘Upright’

Superposition of Waves• Superposition: When 2 waves cross paths.

• Principle of Superposition: When 2 waves meet, the new wave formed is the sum of the two incident waves.

• Interference: the result of wave superposition.

•Link to Superposition animationWave Interference Animations

• 2 waves of same frequency, same direction, different speeds.

• Varying constructive and destructive interference

• 2 waves of same frequency, different direction, same speeds.

• Result is a standing wave (note what’s called the node and anti-node)

• 2 waves of slightly different frequency, same direction, same speeds.

• Result is known as ‘beat’ oscillation.

Standing Waves• Standing waves occur when 2 waves of identical frequency and

speed interfere with one another while travelling in opposite directions.

Node: Point on a wave that doesn’t move.

Anti-Node: Point on wave that moves the most.

Harmonics

1st Harmonic (The Fundamental)2nd Harmonic

3rd Harmonic

Harmonics: Where frequencies are ‘nice’ multiples of the fundamental frequency.

Harmonic # of Nodes # of Antinodes Pattern

1st 2 1

                           

2nd 3 2

                           

3rd 4 3

                           

4th 5 4

                           

5th 6 5

                           

6th 7 6

                           

nth n + 1 n --

Harmonics

Mode Diagrams for Circular Membranes

Diagram Mode Desig. Rel. Frequency Diagram Mode Desig. Rel. Frequency Diagram Mode Desig. Rel. Frequency

How the Vortex Gun WorksWhen you throw a rock through the air, the air moves around it.

http://amasci.com/wing/smring.html