Waves

1. Waves Chapter 15 Pg 454-458 SPI 0707.11.6 & SPI 0707.Inq.4

2. Learning Objectives • Explain the relationship between waves, energy, and matter • Describe the difference between transverse waves and compression waves

3. New Vocabulary • Wave • Vibration • Transverse wave • Crest • Trough • Compressional wave (Longitudinal wave) • Electromagnetic wave

4. What is a wave? • A wave is a disturbance that transfers energy from one place to another without transferring matter • If you throw a rock into a body of water, waves move out from where the rock entered the water • Energy from the splash causes the water to move up and down as the wave passes (disturbance) • Waves transmit energy and not matter • Waves travel through mediums – the materials disturbed by a wave

5. Mechanical Waves • In a water wave, water molecules transfer energy as the molecules exert forces on each other • The types of waves that can travel only through matter (mediums) are called mechanical waves • Mechanical waves are produced by something that is vibrating • A vibration is a repeating back and forth motion

6. Transverse Waves • A wave that makes the matter in a medium move at right angles to the direction the wave moves is a transverse wave • On a transverse wave the high points (peaks) are crests and the low points (valleys) are troughs • Example: shaking a rope up and down • The up and down motion of the rope produces a transverse wave that travels from the hand to the doorknob • Rope moves vertically up and down, while the wave travels horizontally • Motion is at right angles (perpendicular) to the motion of the wave

7. Transverse Waves

8. Compression Waves • Also known as a longitudinal wave • Matter in a medium moves back and forth along the same direction that the wave travels • As a compression wave travels along a spring, the coils of the spring move back and forth • After the wave passes, the coils are in the same place they were before the wave reached them • Only energy is transferred as the wave moves along • Example: a spring or a slinky

9. Parts of Compression Waves • The part of the compression wave where particles are pushed together are called a compression • Parts where the wave particles are spread out are called rarefactions

10. Sound Waves • Sound waves are a type of compression wave • Sound waves are made by something in the air that is vibrating • Sound waves require a medium in order to transfer energy (Air, water, or a solid object) • Figure 5, pg 457 • The stretched-out part of a longitudinal wave is similar to the trough of a transverse wave

11. Electromagnetic Waves • Waves that travel through space where there is no matter are electromagnetic waves • Examples: radio waves, infrared waves, visible light waves, ultraviolet waves, x-rays, gamma rays • The sun emits electromagnetic waves that travel through space to Earth • These waves produce radiant energy • Most of this radiant energy is in the form of infrared and visible light waves • These waves make us feel warm in sunlight and light waves enable us to see

12. Assess What You’ve Learned • Describe the movement of a floating object on a pond when struck by a wave • Explain why a sound wave can’t travel from a satellite to Earth • Compare and contrast a transverse wave and a compression wave. How are they similar/different? • Compare and contrast a mechanical and an electromagnetic wave.