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

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

- 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.

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.

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

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.

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

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

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.

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

End of Section: What Are Waves?

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

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.

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 - 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

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

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.

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

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

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

End of Section: Properties of Waves

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

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.

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

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.

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.

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.

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?

End of Section: Interactions of Waves

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

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.

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

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.

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 misprint. @ 3,700 km = 5 hrs; @ 7 hrs = 5,000 km. Seven hours

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.

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

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.

Click the SciLinks button for links on seismic waves.

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

End of Section: Seismic Waves

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

End of Section: Graphic Organizer