Properties of Waves Waves have energy and transfer energy when they interact with matter They cannot travel through empty space!

Types of Waves Transverse and Longitudinal

Transverse Wave: perpendicular disturbance

Longitudinal Wave: parallel disturbance

Compression and Rarefaction Compression Rarefaction

Distance between the crest of one wave and the crest of the next wave Wavelength Distance between the crest of one wave and the crest of the next wave

Increases with increasing energy Amplitude The height of a wave Increases with increasing energy

Frequency The number of oscillations per second Units of Hertz

Period: time it takes for one complete wave to pass a given point measured in seconds depends on the medium in which the waves are traveling

Period and Frequency Are The Inverse of Each Other Frequency = 1/Period Period= 1/Frequency Gusts of wind cause the Sears Building in Chicago to sway back and forth, completing a cycle every ten seconds. What is its frequency? 1/10Hz What is its period? 10s An electric toothbrush completes 90 cycles every second. What is its frequency? 1/90 hz What is its period? 1s

Wave Motion: Transporting Energy When you talk the energy from your voice travels across the room at about 340 m/s. Wave energy travels through the air. The air itself does not travel at this speed. If it did think how windy it would be!

Wave Speed= Frequency x Wavelength If a train of freight cars, each 10m long, rolls by your at a rate of three cars per second, what is the speed of the train? 30 m/s If a water save vibrates up and down three times each second and the distance between the crests is 2m. What is the frequency? 3 Hz What is the wavelength? 2m What is the speed? 6 m/s

Pitch How high or low a sound is perceived by the human ear. Higher Frequency = Higher Pitch http://www.youtube.com/watch?v=q3v3h_nu_4A

Reflection The bouncing back of waves

Reflection of Sound An Echo

Regular Reflection The angle of incidence and angle of reflection are equal

Irregular or Diffuse Reflection Also known as “scattering.”

Refraction: The bending of a wave due to a change in medium

Refraction of Light

Refraction of Sound During the day the air near the ground is generally warmer than the air above. So the speed of sound near the ground increases. This causes them to bend away from the ground resulting in a sound that doesn’t seem to carry well

Resonance: sounding again When the frequency of vibrations of one object matches the frequency of another. In order for something to resonate, it needs a force to pull it back to its starting position and enough energy to keep it vibrating.

the ability of two or more waves to reinforce or cancel each other Interference the ability of two or more waves to reinforce or cancel each other http://youtube.com/watch?v=0M21_zCo6UM

Resonance and Beats Two identical tuning forks and sounding boxes are placed next to one another. Striking one tuning fork will cause the other to resonate at the same frequency. When a weight is attached to one tuning fork, they are no longer identical. Thus, one will not cause the other to resonate. When two different tuning forks are struck at the same time, the interference of their pitches produces beats.

Diffraction When waves bend or spread out around an obstacle.

Properties of Sound Sound waves are transverse waves

The Doppler Effect and Sound As a sound source mores toward the listener the waves reach the listener with a higher frequency causing the pitch to appear to increase. The opposite occurs as it moves away http://youtube.com/watch?v=imoxDcn2Sgo&feature=related

The Doppler Effect and Light When a light source moves away this is called a red shift. The is due to the decrease towards the red end of the color spectrum. When a light source approaches this is called a blue shift. This is due to the increase toward the high frequency blue end of the color spectrum.

Galaxies appear to be spreading away from a central point Galaxies appear to be spreading away from a central point. Scientists are able to observe this phenomenon and calculate the speed of the galaxies by using the Doppler Effect. What type of color shift would a scientist see from a galaxy moving away? Red Shift

A Distant Star is Spinning Rapidly. Which side would show a blue shift A Distant Star is Spinning Rapidly. Which side would show a blue shift? Which side would show a red shift? The side turning towards us would have a blue shift The side turning away from us would have a blue shift This allows scientists to calculate the spin rate of distant stars.

Bow Waves Waves created when an object moves faster than the waves it creates. Similar to the wake created by a boat.

Shock Waves & Sonic Boom The bow wave of a speedboat that passes by can splash you if you are at the water’s edge. In a sense you can say you were hit by a “water boom.” In the same way, when the conical shell of air behind a supersonic aircraft reaches listeners on the ground, the sharp crack they hear is described as a “sonic boom.”

The Speed of Sound Elasticity Density Temperature Depends on 3 Characteristics of the Medium: Elasticity Density Temperature