Waves

1. Waves

2. Standards • I can compare and contrast the parts of a wave. (0707.11.5) • I can differentiate between transverse and longitudinal waves. (0707.11.6)

3. Waves and Energy • Wave – a disturbance that transfers energy through matter or space • Example: Throwing a pebble into a pond • Where the pebble hits the water, waves move outward from that spot • Energy from the pebble’s splash causes the water to move up and down as the wave passes. • This is known as a disturbance • All waves are disturbances that carry energy from one place to another

4. Waves and Energy • Waves transmit energy but notmatter

5. Waves and Energy • Energy travels through matter but the wave does not transmit it • In other words, the object moves up and then back down to its original position just as you did when doing the wave

6. Waves and Mediums • Many waves require a medium in order to transfer energy (mechanical waves) • Medium – a material that is disturbed by a wave • Examples: air, water, or solid objects • When travelling through a medium, a wave displaces the particles of the medium • The particles do not travel with the wave • They move up and down or back and forth and when the wave passes return to their original resting position

7. Waves and Energy • Example: Stadium wave • Some waves, such as light and radio waves, do not require a medium • Electromagnetic waves – transfer energy through empty space • Example: sunlight

8. Characteristics of a Wave • Amplitude – distance from the midpoint of a wave to its top (crest) or its bottom (trough) • A water wave with high amplitude is a tall wave • A sound wave with high amplitude causes you to hear a loud sound

9. Characteristics of a Wave • Wavelength – distance from any point on a wave to the identical point on the next wave • Crest to crest or trough to trough • Waves with short wavelengths transfer more energy than waves with long wavelengths

10. Characteristics of a Wave • Frequency – number of waves that pass a given point in one second • Frequency and wavelength are inversely related • When one increases, the other decreases • Unit of frequency is the hertz (Hz) • 1 hertz = 1 wave per second • A sound wave with high frequency makes a higher-pitched sound than a sound wave with low frequency

11. Kinds of Waves • Waves are classified as either transverse or longitudinal • This is based on how each kind of wave is transmitted • Transverse wave – particles of the medium vibrate perpendicular to the path of the wave • Example: ocean wave • A transverse wave consists of crests and troughs

12. Kinds of Waves • Longitudinal wave – particles of the medium vibrate parallel to the path of the wave • Example: sound wave • Longitudinal waves are made up of compressions and rarefactions • Compression – part where the particles are pushed together (similar to crest) • Rarefaction – part where the particles are spread apart (similar to trough)

13. Lesson Review • Which of the following is NOT a medium? • Space • Air • Water • Wood

14. Lesson Review • A wave’s amplitude is • The distance from the resting point to a crest or trough • Distance between the crest of one wave and the crest of the next • Distance the wave travels in one second • Number of waves that pass a given point in one second

15. Lesson Review • What do waves transfer? • Matter • Energy • Water • Particles

16. Lesson Review • Picture a tub filled with water and a toy boat floating on the water. You plunge your fist into the water, next to the toy boat. What will happen to the boat? • It will travel to the other end of the tub • It will stay completely still • It will travel closer to your fist • It will bob up and down

17. Lesson Review • Which part of a transverse wave is similar to a compression in a longitudinal wave? • Crest • Trough • Midpoint • Particle