PS Waves

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 What words precede the word wave? What do they have in common?

Connections Represent some sort of back and forth or up and down motion The coming and going of some condition

Does a floating object move with the ripple?

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

Electromagnetic spectrum All use same method to travel All travel at the speed of light

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.

Tsunamis Huge ocean wave Talk more about these in the Earth Science Section of this class

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

Simple harmonic motion Repetitive up and down motion

Damped Harmonic Motion The up and down motion fades over time Result of Friction, Air resistance or internal mechanisms Can be advantageous or not (How So?)