Sound

Vibration a wiggle in time

For example: moving back and forth in the same space, ie., pendulum.

**A vibration exists over time.**

Wave a wiggle in space and time

For example: light and sound

**A wave exists over space and time**Major parts of a wave:Midpoint (Equilibrium)Crests and TroughsCrest (high point)Trough (low point)Amplitude - distance from midpoint to crest or troughHow sound occurs?Sound is a fascinating phenomenon. When something vibrates in the atmosphere, it moves the air particles around it. Those air particles in turn move the air particles around them, carrying the pulse of the vibration through the air. Ourears pick up these fluctuations in air pressure and translate them into electrical signals the brain can process.Electronic sound equipment works the same basic way. It represents sound as a varying electric current. Amplifier

Any device that simply produces a better quality and more powerful version of the audio signal.Frequency (f)how often a vibration occurs(# of crests per second)vibrations per second

Heinrich HertzHeinrich Hertz demonstrated radio waves in 1886.The unit of frequency is the Hertz.1 vibration per second = 1 HertzKilohertz = 1000 v/secMegahertz = 1000000 v/secHow does a radio work?

Frequency and PeriodFrequency and period are reciprocals of each other.Frequency (f) = 1 period f = 1/TPeriod (T) = 1 frequency T = 1/f25.3 Wave MotionSound and light waves move.As waves move, matter is NOT passed along them.

For example:When you create a wave with a rope, it is the disturbance that moves along the rope, not the rope itself.25.4 Wave SpeedHow fast a wave moves depends on the medium of the wave. Wave speed is related to the frequency and wavelength of the wave.v = f*Wave speed (m/s) = frequency (Hz) X wavelength (m)Example:What is the speed of a wave with a frequency of 100 Hz and a wavelength of .025 meters?Answer:v = fSpeed = 100 Hz X .025 mSpeed = 2.5 m/sHow does satellite tv work?25.5 Transverse WavesWaves produced when the motion of the medium is at right angles (PERPENDICULAR) to the direction in which the wave travels.EX: Fishing bobber in a lake

25.6 Longitudinal WavesWaves produced when the particles move ALONG (PARALLEL) the direction of the wave rather than at right angles to itEX: Sound Waves25.7 Interferenceoverlapping waves

Interference Patterns: patterns formed when waves overlap2 types of interference:constructive reinforcing interference when waves align at the crests and troughs**individual effects are increased**Destructive cancellation interferencewhen the crest of one wave aligns with the trough of another**their individual effects are reduced**Interference

The Doppler EffectChristian Doppler (1803-1853)Change in frequency due to the motion of a sound sourceThe Doppler ShiftBlue shift = frequency increases as it approachesRed shift = frequency decreases as it leavesBlue ShiftRed Shift

Higher frequencyLower frequencySonic BOOM the sharp crack heard when the shock wave that sweeps behind a supersonic aircraft reaches the listener.

A slower aircraft sends sound wave crests one at a time and we hear it as a continuous noise.

SoundChapter 26

Answer:

vibrationsWhat causes sounds?

All sounds are made by the vibration of material objects.26.1 The Origin of SoundA vibrating source sends a disturbance through a surrounding medium (such as air) in the form of longitudinal waves.

term that refers to how high or low sound appears to be

PITCHIs it possible to shatter glass with your voice?

High # of vibrations = high frequency = high pitchEX: piccolo

Lower # of vibrations = lower frequency = lower pitchEX: tuba20 - 20,000 Hz

Ultrasonic sound waves above 20,000HzInfrasonic soundwaves below 20 Hz

Humans can hear the range fromWhen a noise occurs, sound travels in all directions

26.2 The Nature of SoundAny medium that waves travel through; may be solids, liquids or gasesUsually, sounds are emitted through air, but they can also pass through solids and liquids26.3 Media that Transmit SoundSolids and liquids are generally much better conductors of sound than air

EX: ever heard motor boats under water?Different mediums carry waves at different speedsSound travels MUCH slower than lightEX: lightening and thunder

The speed of sound at room temperature is 340 m/s

26.4 The Speed of SoundResonance a phenomenon that occurs when the frequency of forced vibrations on an object matches the objects natural frequency, and a dramatic increase in amplitude results26.8ResonanceResonance can occur in structures

EX: marching over bridgesswinging bridges by windResonanceInterference occurs in sound waves. Interference can occur in phase (constructive) or out of phase (destructive)

EX: announcer at a football stadium

26.9InterferenceRipple TankBeat periodic variation in the loudness of sound (different frequencies)

EX: musical instruments out of tune

Musical Beats26.10BeatsWhat is the beat frequency when a 400 Hz and a 405 Hz tuning fork are sounded together?

Answer:Change in frequency = 5 HzTherefore, the beat frequency is 5 beats per secondExample

LIGHT

Chapter 27

we see objects because light bounces off themLight is energy that is emitted by vibrating electric charges in atoms that travel in waves LIGHTSpeed of light = extra distance traveled extra time measured= 300,000,000 km / 1000 sec= 300,000 km/sec27.2 The Speed of Lightlight year the distance traveled by light in one year 9.5 x 1012 km27.2 The Speed of LightWaves by which light energy travelsAll are radiated by vibrating electrons within an atom

27.3 Electromagnetic Waves

27.3 Electromagnetic WavesLight waves are transverse waves.

Polarization the filtering out of all vibrations in a transverse wave, such as a light wave, that are not in a given direction

27.7 PolarizationReflection bouncing off

Refraction penetrating (goes through) and bends