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Chapter 20 Waves. Section 1 What are waves?. A. Rhythmic disturbances that carry energy without carrying matter are called Waves B. Molecules transport wave energy without themselves moving, like a line of people passing a ball. Section 1 What are waves?.
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Chapter 20 Waves
Section 1 What are waves? • A. Rhythmic disturbances that carry energy without carrying matter are called Waves • B. Molecules transport wave energy without themselves moving, like a line of people passing a ball
Section 1 What are waves? • C. Mechanical waves use matter to trasfer energy • 1. Transverse waves- wave energy causes matter in the medium to move up and down or back and forth at right angles to the wave • 2. Compressional waves- matter in the medium moves forward and backward in the same sirection as the wave.
Section 1 What are waves? • D. SoundWaves- Compressional waves caused by colliding air molecules
Section 1 What are waves? • E. Electromagnetic waves- transfer energy without using matter; produced by electrically charged particles
Section 1 What are waves? • Discussion Question: • What is the difference between a mechanical wave and an electromagnetic wave? • Mechanical waves use matter to transfer energy; electromagnetic waves use electriclly charged particles to carry energy
Section 2 Wave Properties • A. Amplitude- a measure of how high wave crests are; the greater the amplitude, the more energy a wave carries
Section 2 Wave Properties • B. Wavelength- distance from the top of one crest to the top of the next crest; or from the bottom of one trough to the bottom of the next trough.
Section 2 Wave Properties • C. Frequency- number of wavelengths passing a given point in one second. • 1. Longer wavelengths result in lower frequencies • 2. Higher frequencies are caused by shorter wavelengths
Section 2 Wave Properties • C. Frequency • 3. Color and Pitch result from wavelengths and frequencies of light and sound.
Section 2 Wave Properties • D. WaveSpeed- how fast a wave travels through a medium. • 1. Mechanical waves travel faster in a medium in which atoms are closer together • 2. Electromagnetic waves travel faster in a medium with fewer atoms in it.
Section 2 Wave Properties • Discussion Question: • Name four properties of waves • Amplitude • Wavelength • Frequency and • Speed
Section 3 Wave Behavior • A. Reflection- When a wave strikes an object and bounces off
Section 3 Wave Behavior • B. Refraction- when a wave bends and changes speed as it moves from one medium to another
Section 3 Wave Behavior • C. Diffraction- the bending of waves around a barrier
Section 3 Wave Behavior • D. Interference- two or more waves combine and form a new wave
Section 3 Wave Behavior • D. Interference • 1. Constructive interference- the crest of one wave overlaps the crest of another wave, making a larger wave • 2. Destructive interference- the crest of one wave overlaps the trough of another wave, making a smaller wave • 3. If waves with equal amplitude meet crest to trough, they cancel each other out
Section 3 Wave Behavior • D. Interference • 4. Interference can be used in hearing protection
Section 3 Wave Behavior • Discussion Question: • How are refraction and diffraction similar and different? • Similar- both involve wave bending; • Different- refraction's bending is caused by a medium change while diffraction's bending is caused by a barrier