2. Nature of Waves Look @ pg. 602! A wave is any disturbance that transmits energy through matter or empty space. Example: water waves in the ocean microwaves inside the microwave oven light waves from the sun radio waves transmitted to the radio sound waves from the radio, telephone, & voices

3. Nature of Waves Most waves transfer energy by the vibration of particles in a medium. A medium is a substance through which a wave can travel. A medium can be a solid, liquid, or gas. Question: You are a commander of a space station located about halfway between Earth and the moon. You are in the Command Center, and your chief of security tells you that sensors have just detected an explosion 61.054 km from the station. How long will it be before you hear the sound of the explosion? Sound waves need a medium through which to travel. If there are no particles to vibrate, no sound is possible! Electromagnetic waves, like visible light, can transfer energy without going through a medium.

4. Nature of Waves Types of Waves: Waves in which the particles vibrate in an up-and-down motion are called transverse waves. The particles in transverse waves move perpendicular to the direction the wave is going. The highest point of a transverse wave is called a crest. The lowest point of a transverse wave is called a trough. All electromagnetic waves are considered transverse waves.

5. Transverse wave… Draw this wave on the front of the “Nature of Waves” flap & label: crest and trough

6. Nature of Waves Types of Waves: In a longitudinal wave, the particles of the medium vibrate back and forth along the path that the wave moves. A part of a longitudinal wave where the particles are crowded together is called a compression. A part of a longitudinal wave where the particles are spread apart is called a rarefaction. A sound wave is an example of a longitudinal wave..

7. Longitudinal Wave Draw this wave on the front of the “Nature of Waves” flap & label: rarefactions and compressions.

8. Properties of Waves The amplitude of a wave is the height of the wave. A wave’s amplitude is the maximum distance that the particles of a medium vibrate from its rest position. Larger amplitude = more energy Smaller amplitude = less energy

9. Properties of Waves A wavelength is the distance between any two crests or compressions next to each other in a wave. The distance between two troughs or rarefactions next to each other is also a wavelength. Shorter wavelength = more energy Longer wavelength = less energy

10. Amplitude and Wavelength Draw and label the properties of a wave: amplitude and wavelength on the front of the “Properties of Waves” flap. Draw and label the properties of a wave: amplitude and wavelength on the front of the “Properties of Waves” flap. You can use pg. 608-609 if you need help. You can use pg. 608-609 if you need help.

11. Bell Work: 3/17/10 1. Draw and label a transverse wave. Be sure that all parts are properly labeled. 2. Draw and label a longitudinal wave. 3. __________ waves vibrate back and forth. 4. ___________ waves vibrate up and down. 5. If you did not finish the last drawing we did yesterday in class, finish drawing and labeling that as well. TCAP Practice Book #25-28 pg. 116-117 TCAP Practice Book #25-28 pg. 116-117

12. Properties of Waves Frequency is the number of waves produced in a given is called the frequency of a wave. Frequency is the number of waves produced in a given amount of time is called the frequency of a wave. Measure the frequency by counting either the number of crests or troughs that pass a point in a certain amount of time. Frequency is expressed in Hertz (Hz). Higher frequency = more energy

13. Properties of Waves Wave speed is the speed at which a wave travels. Wave speed can be calculated by using the following formula: v = λ x f or v = λ f v = wave speed λ = wavelength f = frequency Determine the wave speed of a wave that has a wavelength of 5 m and a frequency of 4 Hz. Express the units as m/s.

14. Wave Interactions Reflection happens when a wave bounces back after hitting a barrier. All waves- including water, sound, and light waves- can be reflected. Light waves reflecting off an object allow you to see the object. Light reflects off surfaces the same way that a ball bounces off the ground. If you throw the ball straight down against a smooth surface, it will bounce straight up. If you bounce it at an angle, it will bounce away at an angle.

15. Wave Interactions Reflection (cont.) A reflected sound wave is called an echo. The light is reflecting off the mirror and back into your eyes so that you are able to see yourself.

16. How does the pencil look broken?

17. Wave Interactions Refraction is the bending of a wave as it passes from one medium to another at an angle. Rainbows are created when sunlight is refracted by water droplets. The water droplets separate white light into the colors of visible light.

18. Wave Interactions The bending of waves around a barrier or through an opening is known as diffraction.

19. Wave Interactions The result of two or more waves overlapping is called interference. If you move a rope at certain frequencies, the rope appears to vibrate in loops. The loops come from the interference between the wave you made and the reflected wave, thus resulting in a standing wave. Certain parts of the wave are always at rest position.

20. Wave Interactions The frequencies at which standing waves are made are called resonant frequencies. When an object vibrating at or near the resonant frequency of a second object causes the second object to vibrate, resonance occurs. A resonating object absorbs energy from the vibrating object and vibrates, too. Tacoma Narrows Bridge AKA “Galloping Gertie” is a phenomenon, or an extraordinary event, that caused a lot of destruction because of resonance. Watch this Video!