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.
Characteristics of Waves
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?
Characteristics of 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?
Characteristics of Waves
Angles
Practice Problem
How many degrees do two right angles contain?
Two right angles contain 180 degrees.
- What Are Waves?
Characteristics of Waves - 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.
Characteristics of Waves - What Are Waves?
Longitudinal Waves
Longitudinal waves move the medium parallel to the direction in which the waves travel.
Characteristics of Waves - What Are Waves?
Longitudinal Waves
The compressions of a longitudinal wave correspond to the crest of a transverse wave. The troughs correspond to rarefactions.
Characteristics of Waves
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?
Characteristics of Waves
Links on Waves
Click the SciLinks button for links on waves.
- What Are Waves?
Characteristics of 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.
Characteristics of Waves
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.
Characteristics of Waves
Wavelength– the distance over which the
wave's shape repeats
Characteristics of Waves
Frequency
Frequency is the number of occurrences of a repeating event per unit time
Characteristics of Waves
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
Characteristics of Waves
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?
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
- Properties of Waves
Characteristics of Waves
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?
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.
- Properties of Waves
Characteristics of Waves
Calculating Frequency
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
- Properties of Waves
Characteristics of Waves
Calculating Frequency
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
- Properties of Waves
Characteristics of Waves
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
- Properties of Waves
Characteristics of Waves
End of Section:Properties of
Waves
Characteristics 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.
Characteristics of Waves - Interactions of Waves
Diffraction
When a wave moves around a barrier or through an opening in a barrier, it bends and spreads out.
Characteristics of Waves - Interactions of Waves
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.
Characteristics of Waves
Wave Interference Activity
Click the Active Art button to open a browser window and access Active Art about wave interference.
- Interactions of Waves
Characteristics of Waves - Interactions of Waves
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.
Characteristics of Waves
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
- Interactions of Waves
Characteristics of Waves
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.
Characteristics of 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
Characteristics of Waves
Motion of a Tsunami
Distance and time
Reading Graphs:
What two variables are plotted on the graph?
- Seismic Waves
Characteristics of 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
Characteristics of 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.
Characteristics of Waves
Seismic Wave Activity
Click the Active Art button to open a browser window and access Active Art about seismic waves.
Characteristics of 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.
Characteristics of Waves
Links on Seismic Waves
Click the SciLinks button for links on seismic waves.
- Seismic Waves
Characteristics of Waves
Seismic Waves
Click the Video button to watch a movie about seismic waves.
- Seismic Waves
Characteristics of Waves
End of Section:Seismic Waves
Characteristics of Waves
Graphic Organizer
Longitudinal
Waves
can be
Transverse
can be
contain contain contain contain
Crests RarefactionsTroughs Compressions
Characteristics of Waves
End of Section:Graphic Organizer