1. Wave Energy

2. Waves and Energy A wave is a disturbance that transfers energy from place to place Energy is defined as the ability to do work Example: A raft in the water – The wave disturbs the surface of the water, which therefore disturbs the raft – The wave’s energy lifts the heavy raft as the wave passes under it – The disturbance caused by the wave is only temporary

3. What Carries Waves? Most kinds of waves need something to travel through The material through which a wave travels through is called a medium – Gases, liquids and solids all act as mediums Waves that require a medium to travel are called mechanical waves Waves that can travel without a medium are called electromagnetic waves – Ex. Light waves from the sun

4. An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelengths and frequencies The longer the wavelength= lower frequencies The shorter the wavelength= higher frequencies The electromagnetic spectrum is a complete range of electromagnetic waves placed in order of increasing frequency

5. How do waves transfer energy? Mechanical waves do not carry the medium – Duck example on page. 511 When a wave enters the medium it transfers energy to the medium’s particles – The particles bump into each other passing the wave’s energy along – Example: when you pass food at the dinner table

6. How to Create a Wave Energy is ALWAYS required to make a wave Mechanical waves are produced when a source of energy causes a medium to vibrate – A vibration is repeated back-and-forth or up-and- down motion – When a vibration moves through a medium a wave is produced Moving objects have energy and they can transfer this energy to a medium to create a wave – Example: Demonstration at the beginning of class

7. Types of Waves Mechanical waves are classified by how they move through mediums There are two types of mechanical waves – 1. Transverse Waves: Are waves that move the medium at right angles to the direction in which the waves travel. – 2. Longitudinal Waves: Are waves that move the medium parallel to the direction in which the wave travels

8. Transverse Waves Transverse means across and the particles of the medium move across or at right angles to the direction of the wave The highpoint of a transverse wave is called the crest The low point is called the trough

9. Longitudinal Waves A spring is an example of a longitudinal wave The part where the coils of the spring are closed together are called compressions The parts where the coils are spread out are called refractions The energy travels from one end of the spring to the other creating a wave After the wave passes each coil returns to the position in which it started

10. Longitudinal Waves Example: Sound Waves – In air sound causes air particles to move back and forth. – In areas where the air particles are close together compressions are formed – In areas between the compressions where air particles are spread out refractions are formed Bill Nye Sound Song Longitudinal Wave Demo Creating a Transverse Wave Demo Creating a Transverse Wave Demo

11. At first I didn't know, yet I was quite intrigued, to learn that sound and light are really forms of energy. But the funny thing about light is it's both particle and wave, so in a cave, I yelled to see how sound behaved! And it came back, it echoed nice, the sound waves bounced back through the air so what I yelled once I heard twice. And so I ran out from the rocks, and I dashed to a telephone, where I picked up the receiver, and I dialed up my home. Hey do you know how sound is made? It's really simple, it happens when something vibrates. Like now you see my vocal chords are moving to and fro, and thus these words I'm saying are just vibrations in my throat! And so I cried, "Sound is a vibe"! It travels through the air in waves and at our ears it then arrives, and then inside these tiny bones, things get all amplified, cause sound's a vibe, sound is a vibe!