the nature of waves ch 20.1 8th
DESCRIPTION
Information obtained from: Holt Science and Technology: Physical Science. New York: Henry Holt & Co, 2007. Print.TRANSCRIPT
Chapter 20 Section 1
Describe how waves transfer energy without transferring the matter.
Distinguish between waves that require a medium and waves that do not.
Explain the difference between transverse and longitudinal waves.
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.”
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.”
Wave: any disturbance that transmits energy through matter or empty space
Energy can be carried away from its source by a wave
The material through which the wave travels does not move with the energy
Consider this…
As a wave travels, it does work on everything in its path
Work is done on the water and anything floating on it’s surface
Ex: Boats and docks bob up and down on the waves
The fact that the objects move tells us the waves are transferring energy
Medium: a substance through which a wave can travel
Most waves transfer energy by the vibration of particles in a medium
A medium can be a solid, liquid, or a gas
Energy is passed from particle to particle
Sound waves need a medium
Ocean waves need a medium
Waves that require a medium are called mechanical waves
Visible light, microwaves, radio waves, x-rays do not require a medium
These waves are called electromagnetic waves
EM waves can go through matter (air, water, glass….)
Energy that reaches the Earth from the Sun comes through EM waves, which go through space
Waves can differ in many ways
Classified based on:The direction in which the particles in the
medium vibrateDirection in which the waves move
2 Main Types of Waves:TransverseLongitudinal
Particles vibrate in a up-and-down motion
“moving across” or perpendicular to the direction the wave is going
Highest point of the wave: crest
Lowest point of the wave: trough
Electromagnetic waves are considered transverse
http://static.howstuffworks.com/gif/noise-canceling-headphone-7.jpg
Particles in the medium travel back and forth along the path that the wave moves
Where the waves are crowded together: compression
Where the particles are spread apart: rarefaction
Example: sound waves
http://static.howstuffworks.com/gif/noise-canceling-headphone-8.jpg
When a wave forms at the boundary of two media a transverse and a longitudinal wave combine to form a surface wave
Look like a transverse wave, but the particles of the medium move in circles
The particles move forward at the crest and backward at the trough
http://www.keele.ac.uk/depts/ma/euromech/rayleigh2.gif http://faculty.gvsu.edu/videticp/wave_animation1.GIF