A wave is a disturbance that travels from one location to another, usually in a median

Different Types of Waves

There are 3 different types of waves

• Transverse Waves

Transverse waves move perpendicular to the direction of travel. They cannot move through a liquid or gas because there is no mechanism for driving motion perpendicular to the propagation of the wave.

• Longitudinal Waves

Longitudinal waves move parallel to the direction traveled. They are capable of traveling through solids and liquids, and are like pulses in a slinky.

• Surface Waves

Surface waves move in circular motions. They are mechanical waves that move along the interface, usually as a gravity wave between two fluids with different densities.

Vocabulary

For Transverse Waves:

Crest- The spot with the maximum amount of positive or upwards displacement

Troughs- The spot with the maximum amount of negative or downwards displacement

Amplitude- The maximum amount of displacement (from rest) of a particle

Wavelength- The length of one complete wave cycle

For Longitudinal Waves:

Compression- The point of maximum density

Rarefaction- The point of minimum density

Wavelength- The length of one complete wave cycle

Nodes- Points of no displacement

Anti-nodes- Points of displacement (opposite of nodes)

For all waves:

Frequency- How often a cycle (one wavelength) occurs

Period- The time to complete one cycle

period=1/frequency frequency=1/period

Examples:

Describe how wavelength and frequency are related. Use full sentences.

Explain why you can't hear sound in space. Use full sentences.

The number of cycles of a periodic wave occurring per unit time is defined as the what?

Speed of Waves

speed=distance/time

A different way of expressing the speed of a wave is:

speed=wavelength/period or velocity=frequency * wavelength

Examples:

A periodic and repeating disturbance in a lake creates waves which emanate outwards from its source to produce circular wave patterns. If the frequency of the source is 2.00 Hz and the wave speed is 5.00 m/s then the distance between adjacent wave crest is _________ meters. Show your work.

What is the frequency of a wave that has a speed of 0.4 m/s and a wavelength of 0.020 meters?

Reflection

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium. Regardless of the angle at which the wavefronts approach the barrier, the waves will always reflect in such a way that the angle at which they approach the barrier equals the angle at which they reflect off the barrier.

Refraction

Refraction of waves involves a change in the direction of waves as they pass from one medium to another, as oppose to a change in direction of waves when they bounce off a barrier. In refraction, there is a change in speed and wavelength of the waves.

Diffraction

In diffraction, there is a change in the direction of waves as they pass through an opening in their path. Water waves are typically an example of diffraction, as they have the ability to travel around corners and through openings.

Doppler Effect

Doppler effect is the apparent change in the frequency of sound as a result of relative motion between the source and the observer. There are eight different Doppler Effect Formulas that are used depending on the case. These formulas are used to find the apparent frequency and wavelength for the different cases of movement between the source and observer.

v(s)=velocity of the source

v(o)=velocity of the observer

v=velocity of sound or light in medium (usually 330 m/s)

f=real frequency

f'=apparent frequency

• When the source is moving towards a observer at rest:

f'=v/v-v(s) * f

• When the source is moving away from the observer at rest:

f'=v/v+v(s) * f

• When the observer is moving towards the stationary source:

f'=v+v(o)/v * f

• When the observer is moving away from a stationary source:

f'=v-v(o)/v * f

• When both the source and observer moves towards each other:

f'=v+v(o)/v-v(s) * f

• When both the source and observer move away from each other:

f'=v-v(o)/v+v(s) * f

• When the source is approaching the stationary observer and the observer is moving away from it:

f'=v-v(o)/v-(s) * f

• When the observer is approaching the stationary source and the source is moving away from it:

f'=v+v(o)/v+v(s) * f

Examples:

A source and listener are moving towards each other with the speed of 54 km/hr. If the true frequency of sound emitted by the source is 500 Hz, calculate the observed frequency when both source and listener are moving towards each other. The velocity of sound in the air is 330 m/s.

Wave Interference

Wave interference occurs when two waves meet while traveling together along the same medium. The interference between the two waves makes the medium take on a shape that results from the net effect of the two individual waves upon the particles of the medium.

There are two types of wave interference:

• Constructive Interference occurs where the two interfering waves have a displacement in the same direction.

• Destructive Interference occurs where the two interfering waves have a displacement in the opposite direction.

Principle of Superposition

The principle of superposition states that:

When two waves interfere, the resulting displacement of the medium at any location is the algebraic sum of the displacement of the individual waves at that same location.