PS 12-10 Waves
Dec 28, 2015
Objectives
• To recognize the relationship between waves and energy
• To distinguish between mechanical waves and electromechanical waves, and longitudinal and transverse waves
• Explain the relationship between particle vibration and wave motion
Connections
• Represent some sort of back and forth or up and down motion
• The coming and going of some condition
What is a wave?
• Is a disturbance that carries energy through matter or space
• It may or may not need a medium to move through, depending on the type of wave
Medium
• The matter through which a wave travels
• Examples, water, air, the Earth are all mediums
• Waves also pass through space, which is not a medium for the most part.
Mechanical waves
• Waves that require a medium
• Almost all waves are mechanical waves
• With one important exception
Light does not require a medium
• Electromagnetic waves do not need a medium
• Move by changing the electric and magnetic fields in space
• Light is the most widely known electromagnetic wave
Waves transfer energy
• We know waves transfer energy because they do Work
• Water waves boat, leaf, surfer…
• Sound waves eardrum
• Light waves on your eye, photographic film
Have you ever been hit by an ocean wave?
• Then you can get the idea that ocean waves can carry a lot of energy.
• Research is underway to find ways to harness energy of ocean waves
• Some of this research is being done at the university of Delaware
Energy from Ocean Waves
• June 2007
Wave Energy Bill Approved by U.S. House Science Committee
Washington, DC [RenewableEnergyAccess.com]
The U.S. House of Representatives Science and Technology Committee has approved, by voice vote, renewable energy legislation that would invest approximately $200 million
in federal funds to advance research and development of wave energy technologies
over the next four years.
Wave Front
• Energy may spread out as a wave travels
• The waves spread out in circles that get bigger
• These circles are called wave fronts
• The energy of a wave front is constant– Gets spread out over a larger area – Less intense at any one point in a larger circle
Ripples
Why you hear• Notes from a singer result from the vocal cords in the throat moving
back and forth
• This move the particles in the air in the throat vibrate
• This vibration creates sound waves that eventually reach your ears
• The vibration of the air in your ears causes your eardrums to vibrate
• The motion of the eardrum triggers a series of electrical pulses to your brain
• Then your brain interprets them as sound
Vibrations
• Involve transformations of energy
• Potential to Kinetic and back
• Think of a weight on the spring