Focus: We will learn how to measure amplitude, wavelength

and frequency.

Waves

The tallest wave ever recorded was 100 ft. tall!

An officer on a ship measured a wave by noticing that it was as high as a specific point on his ship. That point was 100 feet tall!

We can measure parts of all waves.

Height is a property of all waves. All waves have a height that we can measure.

Speed is another property of all waves. All waves move at a speed that we can measure.

Speed Wavelength And frequency

But we’ll talk more about that in a minute!

Other properties of all waves are:

Just like mountains have peaks, and houses have roofs,

The top of a transverse wave is called something special, too. It’s called a CREST.

Parts of a wave

The CREST of a wave is the highest part of a wave.

CREST

The crest of a wave

Every transverse wave has a crest.

Write down your definition of the word “crest,” and draw a picture of a crest.

YOU WILL HAVE1 MINUTE

In your interactive notebook:

The TROUGH of a transverse wave is the lowest part of a wave.

TROUGH

Waves have troughs.

Every transverse wave has a trough.

Write down your definition for the word “trough,” and draw a picture.

YOU HAVE 1 MINUTE

In your interactive notebook:

You are on a boat.The water is startingto get kind of rough.

When your boat is pointing upwards, you are climbing to the crest of the wave.

When your boat is pointing downward and sinking lower, you are falling to the trough of the wave.

Imagine:

The AMPLITUDE is the distance between the middle of the wave (or the resting position) and the crest.

Amplitude

Amplitude

The AMPLITUDE can also be measured by the distance between the middle of the wave and the trough.

Amplitude

Amplitude

The amplitude of a wave is important, because it lets us know how much energy a wave is carrying.

Bigger amplitude = More energy Smaller amplitude = Less energy

Amplitude

What is the amplitude of this wave?

Amplitude

How did you find the amplitude?

Think- Pair – Share

Which wave has the highest amplitude? What is the amplitude of wave A?

Which wave has a higher amplitude?

-2

-1

0

1

2

0 5 10 15

A

B

Compressional Longitudinal

wave

On a compressional wave the area squeezed together is called the compression. The areas spread out are called the rarefaction.

The wavelength is the distance from the center of one compression to the center of the next compression.

Tf

periodfrequency

11

Frequency is the number of waves (vibrations) that pass through a point in one second.

Period is the time it takes for one full wavelength to pass a certain point.

Frequency is waves per second.

Frequency is the number of bumps in a given space or time.

YOU HAVE 2 MINUTES TO ANSWER THE QUESTIONSIN YOUR NOTEBOOK

1. What is the frequency of the wave in the picture on the left? 2. What is the frequency of the wave in the picture on the right?

What is wavelength?

Wavelength is a measure of distance, so the units for wavelength are always distance units, such as meter, centimeters, millimeters, etc.

A wave moving through a medium travels at a certain speed.

Wave speed is usually measured in meters/second

Wave speed = frequency x wavelength.

Try it out!!

1. A wave is 8 meters long and has a frequency of 3 Hz. Find speed.

2. In the ocean, a wave has a wavelength of 4 m and a frequency of 2 Hz. What is the wave’s speed?