Characteristics of Waves What Are Waves? Properties of Waves Interactions of Waves Seismic Waves Table of Contents

Characteristics of Waves

What Are Waves?

Properties of Waves

Interactions of Waves

Seismic Waves

Table of Contents

Characteristics of Waves - What Are Waves?

Waves and Energy

Waves travel through water, but they do not carry the water (or the duck) with them.


Angles An angle is formed when two lines meet at a point. Angles are measured in degrees, indicated by the symbol º. A circle has 360 degrees. A right angle is an angle that contains 90 degrees. Two lines that meet at a point to form a 90º angle are said to be perpendicular to each other.

- What Are Waves?


Angles

Practice Problem

Draw a circle on a piece of paper. How many right angles can you fit in the circle?

Four right angles can fit in a circle.

- What Are Waves?


Angles

Practice Problem

How many degrees do two right angles contain?

Two right angles contain 180 degrees.

- What Are Waves?


Transverse Waves

Waves that move the medium at right angles to the direction in which the waves travel are called transverse waves.


Longitudinal Waves

Longitudinal waves move the medium parallel to the direction in which the waves travel.


Longitudinal Waves

The compressions of a longitudinal wave correspond to the crest of a transverse wave. The troughs correspond to rarefactions.


What You Know

What You Learned

Using Prior KnowledgeBefore you read, look at the section headings and visuals to see what this section is about. Then write what you know about waves and energy in a graphic organizer like the one below. As you read, write what you learn.

1. Waves are high and low.2. Waves move things up and down.

1. Mechanical waves can be transverse waves or longitudinal waves.

2. Transverse waves move the medium up or down or side to side, and they have crests and troughs.

3. Longitudinal waves move the medium back and forth, and they have compressions and rarefactions.

- What Are Waves?


Links on Waves

Click the SciLinks button for links on waves.

- What Are Waves?


End of Section:What Are Waves?

Characteristics of Waves - Properties of Waves

Amplitude, Wavelength, and Frequency

The basic properties of all waves are amplitude, wavelength, and frequency.


AmplitudeAmplitude is the magnitude of the wave. How much

the particles move in a wave from the resting position. It is a measure of the amount of energy in

the wave.


Wavelength– the distance over which the

wave's shape repeats


Frequency

Frequency is the number of occurrences of a repeating event per unit time


Calculating Frequency

The speed of a wave on a rope is 50 cm/s and its wavelength is10 cm. What is the wave’s frequency?

Read and Understand

What information have you been given?

Speed = 50 cm/s

Wavelength = 10 cm

- Properties of Waves




Plan and Solve

What quantity are you trying to calculate?

The frequency of a wave = __ Hz

What formula contains the given quantities and the unknown quantity?

Frequency = Speed/Wavelength

Perform the calculation.

Frequency = Speed/Wavelength = 50 cm/s/10 cm

Frequency = 5/s = 5 Hz





Look Back and Check

Does your answer make sense?

The wave speed is 50 cm per second. Because the distance from crest to crest is 10 cm, five crests will pass a point every second.




Practice Problem

A wave has a wavelength of 2 mm and a frequency of 3 Hz. At what speed does the wave travel?

(2 mm)(3 Hz) = 6 mm/s




Practice Problem

The speed of a wave on a guitar string is 142 m/s and the frequency is 110 Hz. What is the wavelength of the wave?

(142 m/s)/(110 Hz) = 1.3 m



OutliningAn outline shows the relationship between main ideas and supporting ideas. As you read, make an outline about the properties of waves that you can use for review. Use the red headings for the main ideas and the blue headings for the supporting ideas.

Properties of Waves

I. AmplitudeA. Amplitude of

Transverse WavesB. Amplitude of

Longitudinal WavesII. WavelengthIII. FrequencyIV. Speed



End of Section:Properties of

Waves


When an object or wave hits a surface through which it cannot pass, it bounces back.

- Interactions of Waves

Reflection

Characteristics of Waves - Interactions of Waves

Refraction

When a wave enters a new medium at an angle, one side of the wave changes speed before the other side, causing the wave to bend.


Diffraction

When a wave moves around a barrier or through an opening in a barrier, it bends and spreads out.


Interference

The interference that occurs when waves combine to make a wave with a larger amplitude is called constructive interference.

The interference that occurs when waves combine to make a wave with a smaller amplitude is called destructive interference.


Wave Interference Activity

Click the Active Art button to open a browser window and access Active Art about wave interference.



Standing Waves

If the incoming wave and a reflected wave have just the right frequency, they produce a combined wave that appears to be standing still.


Question Answer

Asking QuestionsBefore you read, preview the red headings. In a graphic organizer like the one below, ask a what, how, when, or where question for each heading. As you read, write answers to your questions.

How are waves reflected? Waves are reflected when they hit a surface through which they cannot pass and bounce back.

What is refraction? The bending of waves due to a change in speed

When does diffraction occur? When a wave moves around a barrier or through an opening in a barrier

What is a standing wave? A wave that appears to stand in one place even though it is really two waves interfering



End of Section:Interactions of

Waves

Characteristics of Waves - Seismic Waves

Types of Seismic Waves

Seismic waves include P waves, S waves, and surface waves.


Motion of a Tsunami

This graph shows the rate at which a tsunami moves across the Pacific Ocean. Use the data plotted on the graph to answer the following questions.

- Seismic Waves


Motion of a Tsunami

Distance and time

Reading Graphs:

What two variables are plotted on the graph?

- Seismic Waves


Motion of a Tsunami

In two hours, the tsunami travels 1,500 km; in four hours, it travels 3,000 km.

Interpreting Data:

How far does the tsunami travel in two hours? In four hours?

- Seismic Waves


Motion of a Tsunami

Seven hours

Predicting:

Easter Island is 3,700 kilometers from the earthquake. How many hours would it take the tsunami to reach Easter Island?

- Seismic Waves

Characteristics of Waves - Seismic Waves

Types of Seismic Waves

Earthquakes that occur underwater, like the one off the coast of Chile in 1960, can produce huge surface waves on the ocean called tsunamis.


Seismic Wave Activity

Click the Active Art button to open a browser window and access Active Art about seismic waves.


Building VocabularyUsing a word in a sentence helps you think about how to best explain the word. After you read the section, carefully note the definition of each Key Term. Also note other details in the paragraph that contains the definition. Use all this information to write a meaningful sentence using the Key Term.

- Seismic Waves

Key Terms: Examples:seismic wave A seismic wave is produced by an earthquake.

P wave A P wave is a longitudinal seismic wave.

S wave An S wave is a transverse seismic wave.

surface wave A surface wave is a combination of a longitudinal wave and a transverse wave that travels along the surface of a medium.

Key Terms: Examples:tsunami

seismograph

A tsunami is a huge surface wave on the ocean caused by an underwater earthquake.

A seismograph is an instrument used to detect and measure earthquake waves.


Links on Seismic Waves

Click the SciLinks button for links on seismic waves.

- Seismic Waves


Seismic Waves

Click the Video button to watch a movie about seismic waves.

- Seismic Waves


End of Section:Seismic Waves


Graphic Organizer

Longitudinal

Waves

can be

Transverse

can be

contain contain contain contain

Crests RarefactionsTroughs Compressions


End of Section:Graphic Organizer

Documents

Characteristics of Waves What Are Waves? Properties of Waves Interactions of Waves Seismic Waves Table of Contents