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Information obtained from: Holt Science and Technology: Physical Science. New York: Henry Holt & Co, 2007. Print.

### Transcript of The Nature of Waves Ch 20.1 8th

Chapter 20 Section 1

y Describe how waves transfer energy without

transferring the matter.y Distinguish between waves that require a medium and

waves that do not.y Explain the difference between transverse and

longitudinal waves.

y How many waves??

Imagine that your family has just returned from a day at the beach. You had fun playing in the ocean under a hot sun. You put some cold pizza in the microwave for dinner, and you turn on the radio. Just then, the phone rings. It s your friend calling to ask about homework.

y At least 5!!!!

Imagine that your family has just returned from a day at the beach. You had fun playing in the ocean under a hot sun. You put some cold pizza in the microwave for dinner, and you turn on the radio. Just then, the phone rings. It s your friend calling to ask about homework.

y Wave: any disturbance that transmits energy through

matter or empty spacey Energy can be carried away from its source by a wave y The material through which the wave travels does not

move with the energyy Consider this

y As a wave travels, it does work on everything in its path y Work is done on the water and anything floating on

it s surfacey Ex: Boats and docks bob up and down on the waves y The fact that the objects move tells us the waves are

transferring energy

y Medium: a substance through which a wave can

travely Most waves transfer energy by the vibration of

particles in a mediumy A medium can be a solid, liquid, or a gas y Energy is passed from particle to particle

y Sound waves need a medium y Ocean waves need a medium y Waves that require a medium are called mechanical

waves

y Visible light, microwaves, radio waves, x-rays do not

require a mediumy These waves are called electromagnetic waves

y EM waves can go through matter (air, water, glass .) y Energy that reaches the Earth from the Sun comes

through EM waves, which go through space

y Waves can differ in many ways y Classified based on:y The direction in which the particles in the medium

vibrate y Direction in which the waves movey 2 Main Types of Waves:y Transverse y Longitudinal

y Particles vibrate in a up-and-down motion y moving across or perpendicular to the direction the

wave is goingy Highest point of the wave: crest y Lowest point of the wave: trough y Electromagnetic waves are considered transverse

y Particles in the medium travel back and forth along

the path that the wave movesy Where the waves are crowded together: compression y Where the particles are spread apart: rarefaction y Example: sound waves