Topic: Properties of Waves

• Essential Question: What vocabulary do we use to accurately describe the properties of waves and how they interact with other waves or objects?

What is a wave?

• Waves• Medium• Resonance• Interference

• Constructive interference• Destructive Interference

• Transverse Wave• Longitudinal Wave

• Amplitude• Frequency• Period

• Wavelength• Reflection• Refraction• Diffraction• Polarization• Phase

• Doppler Effect• Node

• Antinode

What is a wave?

• Wave:– A rhythmic disturbance that carries energy

through matter or space• Wave Pulse:– A single bump or disturbance that travels through

a medium

What is a wave?

• Waves• Medium• Resonance• Interference

• Constructive interference• Destructive Interference

• Transverse Wave• Longitudinal Wave

• Amplitude• Frequency• Period

• Wavelength• Reflection• Refraction• Diffraction• Polarization• Phase

• Doppler Effect• Node

• Antinode

What is a medium?

• Medium:– Something that the wave travels through.

• Examples:– The medium of the waves in yesterday’s lab was

the beads.– The medium of an ocean wave is water.– What medium do sound waves travel through?

IMPORTANT!

• THE MEDIUM DOESN’T GO ANYWHERE!– The medium only moves back and forth or up and

down, but on average, it stays in the same place!– Don’t believe me? Watch the green beads in te

simulation from the lab:

Describing Waves:

• Waves• Medium• Resonance• Interference

• Constructive interference• Destructive Interference

• Transverse Wave• Longitudinal Wave

• Amplitude• Frequency• Period

• Wavelength• Reflection• Refraction• Diffraction• Polarization• Phase

• Doppler Effect• Node

• Antinode

Parts of a Wave

Describing Waves:

• Amplitude:– The height of the wave– Measured from the MIDDLE – where the medium

would be if there was no wave passing through it. • Wavelength:– Measured in meters. Represented by λ

Describing Waves:

• Waves• Medium• Resonance• Interference

• Constructive interference• Destructive Interference

• Transverse Wave• Longitudinal Wave

• Amplitude• Frequency• Period

• Wavelength• Reflection• Refraction• Diffraction• Polarization• Phase

• Doppler Effect• Node

• Antinode

• Frequency:– The number of complete oscillations/cycles it

makes each second– f = 1/T

f = frequency (units of Hz or 1/s) T = period (units of s) – the time for one complete

cycle

Speed of a wave

So frequency is not the speed of the wave. Formula:

v = λfλ = wavelength (meters)f = frequency (1/s or Hz)units = m/s

Types of Waves:

• Waves• Medium• Resonance• Interference

• Constructive interference• Destructive Interference

• Transverse Wave• Longitudinal Wave

• Amplitude• Frequency• Period

• Wavelength• Reflection• Refraction• Diffraction• Polarization• Phase

• Doppler Effect• Node

• Antinode

Types of Waves

– Transverse wave – a wave that vibrates perpendicular to the direction of wave motion

– Longitudinal wave – a wave that moves parallel to the disturbance.• Example: Sound wave

What kind of wave is this?

What kind of wave is this?

More Terminology• Antinode – Where the largest displacement

is located in a wave (largest amplitude)• Node – Where the smallest displacement is

located in a wave (smallest amplitude)• Standing wave:– When a wave appears to be standing still

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Wave Interference

• Destructive interference:– When two waves collide and

result in a smaller wave• Constructive interference:– When two waves collide and

result in a larger wave• Principle of superposition:– The algebraic sum of the

heights two waves that collide is equal to the height of the resulting wave

Principle of superposition

• When two waves collide, or interfere, they add together.

• The blue wave and the green wave add together to make the black wave

Wave Interaction Terminology

• Incident wave – A wave that strikes a boundary

• Reflected wave – A wave that returns after striking a boundary

Other Wave Interactions

• Reflection:– When a wave bounces off an object– Law of Reflection – The angle of incidence is equal

to the angle of reflection.

• Refraction:– The change in direction of a wave at the boundary

between two different media

• Diffraction– The spreading of waves around the edge of a

barrier or through a hole.– Often results in a planar wave changing into a

circular wave