1. Table of Contents What Are Waves? Properties of Waves
Interactions of Waves
Seismic Waves

2. Waves and Energy - What Are Waves?
Waves travel through water, but they do not carry the water (or the duck) with them.

3. - What Are 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.

4. Angles - What Are Waves? 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.

5. Angles - What Are Waves? Practice Problem
How many degrees do two right angles contain?
Two right angles contain 180 degrees.

6. Transverse Waves - What Are Waves?
Waves that move the medium at right angles to the direction in which the waves travel are called transverse waves.

7. Longitudinal Waves - What Are Waves?
Longitudinal waves move the medium parallel to the direction in which the waves travel.

8. Longitudinal Waves - What Are Waves?
The compressions of a longitudinal wave correspond to the crest of a transverse wave. The troughs correspond to rarefactions.

9. Using Prior Knowledge - What Are Waves?
Before 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.
What You Know
Waves are high and low.
Waves move things up and down.
What You Learned
Mechanical waves can be transverse waves or longitudinal waves.
Transverse waves move the medium up or down or side to side, and they have crests and troughs.
Longitudinal waves move the medium back and forth, and they have compressions and rarefactions.

10. Click the SciLinks button for links on waves.
- What Are Waves?
Links on Waves
Click the SciLinks button for links on waves.

11. End of Section: What Are Waves?

12. Amplitude, Wavelength, and Frequency
- Properties of Waves
Amplitude, Wavelength, and Frequency
The basic properties of all waves are amplitude, wavelength, and frequency.

13. Amplitude
Amplitude 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.

14. Wavelength
– the distance over which the wave's shape repeats

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

16. Calculating Frequency
- Properties of Waves
Calculating Frequency
The speed of a wave on a rope is 50 cm/s and its wavelength is 10 cm. What is the wave’s frequency?
Read and Understand
What information have you been given?
Speed = 50 cm/s
Wavelength = 10 cm

17. Calculating Frequency
- Properties of Waves
Calculating Frequency
The speed of a wave on a rope is 50 cm/s and its wavelength is 10 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

18. Calculating Frequency
- Properties of Waves
Calculating Frequency
The speed of a wave on a rope is 50 cm/s and its wavelength is 10 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.

19. Calculating Frequency
- Properties 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

20. Calculating Frequency
- Properties 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

21. Outlining - Properties of Waves
An 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.
Amplitude
Amplitude of Transverse Waves
Amplitude of Longitudinal Waves
Wavelength
Frequency
Speed

22. End of Section: Properties of Waves

23. Reflection - Interactions of Waves
When an object or wave hits a surface through which it cannot pass, it bounces back.

24. Refraction - Interactions of Waves
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.

25. Diffraction - Interactions of Waves
When a wave moves around a barrier or through an opening in a barrier, it bends and spreads out.

26. Interference - Interactions of Waves
The interference that occurs when waves combine to make a wave with a smaller amplitude is called destructive interference.
Interference
The interference that occurs when waves combine to make a wave with a larger amplitude is called constructive interference.

27. Wave Interference Activity
- Interactions of Waves
Wave Interference Activity
Click the Active Art button to open a browser window and access Active Art about wave interference.

28. Standing Waves - Interactions of 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.

29. Asking Questions - Interactions of Waves
Before 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.
Question
Answer
How are waves reflected?
Waves are reflected when they hit a surface through which they cannot pass and bounce back.
The bending of waves due to a change in speed
What is refraction?
When a wave moves around a barrier or through an opening in a barrier
When does diffraction occur?
A wave that appears to stand in one place even though it is really two waves interfering
What is a standing wave?

30. End of Section: Interactions of Waves

31. Types of Seismic Waves - Seismic Waves
Seismic waves include P waves, S waves, and surface waves.

32. Motion of a Tsunami - Seismic Waves
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.

33. Motion of a Tsunami - Seismic Waves Reading Graphs:
What two variables are plotted on the graph?
Distance and time

34. Motion of a Tsunami - Seismic Waves Interpreting Data:
How far does the tsunami travel in two hours? In four hours?
In two hours, the tsunami travels 1,500 km; in four hours, it travels 3,000 km.

35. Motion of a Tsunami - Seismic Waves Predicting:
Easter Island is 3,700 kilometers from the earthquake. How many hours would it take the tsunami to reach Easter Island?
Possible 3,700 km = 5 7 hrs = 5,000 km.
Seven hours

36. Types of Seismic Waves - 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.

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

38. Building Vocabulary - Seismic Waves
Using 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.
Key Terms:
Examples:
tsunami
seismograph
Key Terms:
Examples:
seismic wave
A tsunami is a huge surface wave on the ocean caused by an underwater earthquake.
A seismic wave is produced by an earthquake.
P wave
A P wave is a longitudinal seismic wave.
A seismograph is an instrument used to detect and measure earthquake waves.
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.

39. Click the SciLinks button for links on seismic waves.

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

41. End of Section: Seismic Waves

42. Graphic Organizer Waves Transverse Longitudinal Crests Troughs
can be
can be
Transverse
Longitudinal
contain
contain
contain
contain
Crests
Troughs
Compressions
Rarefactions

43. End of Section: Graphic Organizer