What are waves? A disturbance that travels through matter or space They transfer energy from place to place but do not transfer matter. A wave transfers energy without transferring matter from one place to another. EX: In water, energy in waves move but the water molecules move only a short distance. Vibrating objects create waves
What do waves travel through Medium – the material through which waves travel. They travel through types of Matter – solids, liquids or gas Or Space The speed of the wave depends on the medium they travel through
What are the types of waves Mechanical – only travel through matter Can be transverse or longitudinal In transverse – the particles move perpendicular to the energy of the wave - Water waves In longitudinal – the particles move parallel - sound waves Electromagnetic – travel through matter and space – Don’t need a medium to travel through - light waves
How do we describe waves? Amplitude - measure of how far particles in the medium are from their normal rest position. (the maximum displacement from resting position) As a wave passes, particles vibrate up and down or back and forth in the medium Crests = highest points Troughs = lowest point
What is this wave’s amplitude?
Amplitude Which has a larger amplitude A or B? Why?
2 Wavelength distance over which the wave’s shape repeats Distance from any point on a wave to the same point later on the wave Ex crest to crest, or trough to trough.
What is this wave’s wavelength?
3. Frequency – number of crests (or troughs) that pass per unit of time Wave period – is the amount of time for one wavelength to pass a given point Ex/ time between 2 crests Frequency gives a unit of time Ex/ # of crests per second Measured in Hertz = 1 Hz = 1 wavelength per second
If 1 second passes, what is the frequency of Wave A? Wave B?
What affects the energy of a wave? Amplitude – high amplitude = high energy Frequency – (in EM waves), high frequency = high energy X-rays = high radio waves = low Waves lose energy due to friction and wave spreading – movement in all directions.
You just came home from a day at the beach You just came home from a day at the beach. You swam in the ocean and stretched out in the sunlight. Your friend brought a radio so you could listen to music. When you arrived home, you heated some pizza in the microwave oven. As you waited for it to cook, you turned on the TV, and then the phone rang. List examples of the waves in the story AND classify as mechanical or electromagnetic
Longitudinal Wave Compressional Wave wave particles vibrate back and forth along the path that the wave travels. Compressional Wave
Compressions The close together part of the wave Rarefactions The spread-out parts of a wave
Transverse waves wave particles vibrate in an up-and-down motion.
Transverse waves Crests Highest part of a wave Troughs The low points of the wave
Waves transfer energy without transferring matter. Frequency= waves/time
Wave Velocity - is the speed with which a wave crest passes by a particular point in space It is measured in meters/second. Wave Velocity = Frequency Wavelength
Speed of Sound air (0 C) 331 water (25 C) 1493 sea water 1533 Medium velocity m/sec air (20 C) 343 air (0 C) 331 water (25 C) 1493 sea water 1533 diamond 12000 iron 5130 copper 3560 glass 5640