Behavior of Waves

Properties of Waves

Amplitude and Energy

• When a medium is at rest position, it is not moving. 

• Any amount of energy that moves through a medium will cause a mechanical wave. Depending on the amount of energy moving through the medium, the wave can be small to quite large. Consider the size of the wave that is caused by a pebble being thrown in to a pond of water. Then consider the waves caused by tsunamis (very large ocean waves caused by underwater earthquakes or volcanic eruptions).

Example of a tsunami

Small waves on surface of water

Amplitude and Energy

• The differences in the sizes of the waves has to do with the amount of energy moving through the medium.

• Amplitude is the maximum distance the particles in a medium move from their rest position as the wave passes through the medium.

• Another good definition for amplitude would be : the measure of the energy in a wave.

Amplitude and Energy

• The amount of energy moving through a medium determines the size of the wave.

• A small amount of energy will create a smaller wave.

• A large amount of energy will create a larger wave.

• Waves with more energy have higher amplitudes.

• Waves with less energy have lower amplitudes.

Multiple Choice

True of False.

John threw a small pebble into a pond and created a wave with a very high amplitude.

• True

• False

Multiple Choice

True or False.

Amplitude is a measure of the number of waves caused by energy.

• True

• False

Amplitude and Transverse Waves

Amplitude in a transverse wave is measured by the distance from the rest position of the medium to one of the crests or troughs

Amplitude and Transverse Waves

Waves that have larger amplitude have more energy. Waves that have smaller amplitude have less energy.

Multiple Choice

For a wave, the _____ the amplitude, the _____ energy the wave carries.

• Larger,more

• Smaller, more

• Larger, less

• Smaller, less

Amplitude and Longitudinal (Compressional) Waves

In a longitudinal wave that has a large amplitude, the particles in the compressions are close together and the rarefactions are far apart.

Multiple Choice

In a longitudinal wave that has a large amplitude, the particles in the compressions are ______ and the rarefactions are _____.

• far apart, close together

• close together, far apart

Wavelength

• A wavelength is the distance from one point on a wave to the same point on the next wave.

• In a transverse wave, measure the distance from crest to crest and from trough to trough

• In a longitudinal wave, measure from one compression to compression and from rarefaction to rarefaction.

Frequency

• The frequency is the number of waves that pass by a point each second.

• Determined by how much the medium vibrates

• Faster vibrations will result in higher frequency

Wavelength and Frequency

• When the frequency of a wave changes, the wavelength also changes

• Longer wavelength have a lower frequency

• shorter wavelength have a higher frequency

Multiple Choice

In a transverse wave, wavelength is measured ________________.

• from compression to compression

• from rarefaction to rarefaction

• from crest to trough

• from trough to trough or crest to crest

Multiple Choice

To say that a wave has a frequency of 2Hz is the same as saying that __________.

• two waves pass the same point every two seconds.

• two waves pass the same point every one second.

• two waves pass the same point every day.

• two waves pass the same point every week.

Multiple Select

Which two of the following statements is true about wavelength and frequency?

• The longer the wavelength, the higher the frequency.

• The shorter the wavelength, the lower the frequency.

• The longer the wavelength, the lower the frequency.

• The shorter the wavelength, the higher the frequency.