Wave Property and Speed

T3L1- Properties of Waves

by PAE 4

​Recap: The parts of a wave

Multiple Choice

Name the missing part of the wave

• Amplitude

• Wavelength

Multiple Choice

Name the missing part of the wave ....?

• Wavelength

• Amplitude

​The wavelength is the length of a complete wave cycle. Here it is the distance between the crests.

​The period ,(T) is the time it takes to complete one wavelength.

​Can you measure the period here? What's the best way?

​Here are two types of waves... can you remember what they are called?

Multiple Choice

This type of wave is called a...

• Longitudinal wave, because it's particle motion is parallel to direction of wave travel

• Transverse wave, because it's particle motion is perpendicular to the direction of wave travel

Multiple Choice

This type of wave is called a...

• Longitudinal wave, because it's particle motion is parallel to direction of wave travel

• Transverse wave, because it's particle motion is perpendicular to the direction of wave travel

​Frequency is a measure of how often something happens in a given time period.

​

​For example, if you go shopping every Monday. Your frequency of shopping is once per week.

​

​If you go shopping every Monday and Friday, then your frequency is twice per week.

​Let's talk about frequency...

​A wave's frequency (f) is the amount of wavelengths that pass a point in a certain amount of time.

​

​It is most often represented in units of 'per second' or '1/second' or Hertz (Hz)

​So, if 1 complete wavelength passes a point at every second, its frequency is '1 per second' or '1 Hertz'.

​And if 320 wavelengths pass a point at every second, its frequency is 320 Hz.

​A wave's frequency (f) is the amount of wavelengths (λ) that pass a point in a certain amount of time.

​

​It is most often represented in units of 'per second' or '1/second' or Hertz (Hz)

​So, if 1 complete wavelength passes a point at every second, its frequency is '1 per second' or '1 Hertz'.

​And if 320 wavelengths pass a point at every second, its frequency is 320 Hz.

Multiple Choice

Which of the following travelling waves has a higher frequency?

• A

• B

• C

​There is an important relationship between, speed, wavelength and frequency.

​Suppose that the 2 lanes above are moving with the same velocity. Will there be more cars or trucks passing the arrow after a given amount of time?

​Like the cars and trucks, these waves are propagating at the same speed.

​What can you conclude about the relationship between wavelength, λ and frequency­, f ?

Multiple Choice

What can you conclude about the relationship between wavelength and frequency by observing them?

• Wavelength and frequency are unrelated

• When wavelength increases, the frequency decreases.

• When wavelength increases, the frequency also increases.

​The speed that a wave propagates is called the wave speed, v

​Wave speed

​How could we represent the wave speed using wavelength λ and period T?

Multiple Choice

​How could we represent the wave speed using wavelength λ and period T?

• $$v=\frac{\lambda}{T}$$  

• $$v=\frac{T}{\lambda}$$  

• $$v=\lambda\cdot T$$  

​So, now... we know that wave speed is:

​From the previous slides, we also know that frequency f is the number of waves that pass a point per unit time. And that it is represented by '1/sec' or Hz.

​But now, if instead of seconds, we replaced the time with the period T, the frequency f becomes...

​Now we can replace the period T in the formula for wave speed with frequency f ...

​That's a wrap...

​Use the following image to answer questions 3-6

Multiple Choice

What is labeled "A" in Gabriella's model?

• Amplitude

• Crest

• Trough

• Wavelength

Multiple Choice

What is labeled "B" in Gabriella's model?

• Amplitude

• Wavelength

• Trough

• Crest

Multiple Choice

What is labeled "C" in Gabriella's model?

• Amplitude

• Wavelength

• Trough

• Crest

Multiple Choice

What is labeled "D" in Gabriella's model?

• Amplitude

• Wavelength

• Trough

• Crest

Multiple Choice

When modeling waves, a transverse wave moves______ to the particle motion. A longitudinal wave moves in the same direction as the particle in motion

• parallel

• perpendicular 

Multiple Choice

When modeling waves, a transverse wave moves perpendicular to the particle motion. A _____ wave moves in the same direction as the particle in motion

• taller

• longitudinal

​Use the following chart to answer questions 10-15

Multiple Choice

Armando used yarn to create waves on sheets of graph paper. He recorded his wave data in the table.

Which heading in the table describes wavelength?

• Wave

• Number of crests

• distance between crests

• height of crests

Multiple Choice

The height of the crest represents the____ of a wave. Based on the evidence in the table, the height of the wave is not dependent on the frequency 

• frequency

• wavelength

• amplitude

Multiple Choice

The height of the crest represents the amplitude  of a wave. Based on the evidence in the table, the height of the wave is not dependent on the ____.

• wave speed

• frequency