Major parts of a wave:

Vibration – a wiggle in timeFor example: moving back and forth in the same space, ie., pendulum. **A vibration exists over time.**

Wave – a wiggle in space and timeFor example: light and sound**A wave exists over space and time**

Major parts of a wave: Midpoint (Equilibrium)

Crests and Troughs Crest (high point) Trough (low point)

Amplitude - distance from midpoint to crest or trough

How 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 Hertz Heinrich Hertz demonstrated radio waves in 1886. The unit of frequency is the Hertz. 1 vibration per second = 1 Hertz Kilohertz= 1000 v/sec Megahertz= 1000000 v/sec How does a radio work?

Frequency and Period • Frequency and period are reciprocals of each other. • Frequency (f) = 1  period • f = 1/T • Period (T) = 1  frequency • T = 1/f

25.3 Wave Motion • Sound 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 Speed How 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 = fλ Speed = 100 Hz X .025 m Speed = 2.5 m/s How does satellite tv work?

25.5 Transverse Waves Waves 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 Waves Waves produced when the particles move ALONG (PARALLEL) the direction of the wave rather than at right angles to it EX: Sound Waves

25.7 Interference overlapping waves Interference Patterns: patterns formed when waves overlap

2 types of interference: • constructive – reinforcing interference when waves align at the crests and troughs **individual effects are increased**

Destructive– cancellation interference when the crest of one wave aligns with the trough of another **their individual effects are reduced**

Interference

The Doppler Effect • Christian Doppler (1803-1853) • Change in frequency due to the motion of a sound source

The Doppler Shift Blue shift = frequency increases as it approaches Red shift = frequency decreases as it leaves

Blue ShiftRed Shift Lower frequency Higher frequency

Sonic 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.

Sound Chapter 26

What causes sounds? Answer: vibrations

26.1The Origin of Sound All sounds are made by the vibration of material objects.

A vibrating source sends a disturbance through a surrounding medium (such as air) in the form of longitudinal waves.

PITCH term that refers to how high or low sound appears to be Is it possible to shatter glass with your voice?

High # of vibrations = high frequency = high pitch EX: piccolo Lower # of vibrations = lower frequency = lower pitch EX: tuba

Humans can hear the range from 20 - 20,000 Hz Ultrasonic – sound waves above 20,000Hz Infrasonic – soundwaves below 20 Hz

26.2 The Nature of Sound • When a noise occurs, sound travels in all directions

26.3 Media that Transmit Sound Any medium that waves travel through; may be solids, liquids or gases Usually, sounds are emitted through air, but they can also pass through solids and liquids

Different mediums carry waves at different speeds • Solids and liquids are generally much better conductors of sound than air EX: ever heard motor boats under water?

26.4 The Speed of Sound • Sound travels MUCH slower than light EX: lightening and thunder • The speed of sound at room temperature is  340 m/s

26.8Resonance Resonance– a phenomenon that occurs when the frequency of forced vibrations on an object matches the object’s natural frequency, and a dramatic increase in amplitude results

Resonance Resonance can occur in structures EX: marching over bridges swinging bridges by wind

26.9Interference Interference occurs in sound waves. Interference can occur “in phase” (constructive) or “out of phase” (destructive) EX: announcer at a football stadium Ripple Tank

26.10Beats Beat – periodic variation in the loudness of sound (different frequencies) EX: musical instruments out of tune Musical Beats

Example What is the beat frequency when a 400 Hz and a 405 Hz tuning fork are sounded together? Answer: Change in frequency = 5 Hz Therefore, the beat frequency is 5 beats per second

LIGHT Chapter 27

LIGHT • we see objects because light bounces off them • Light is energy that is emitted by vibrating electric charges in atoms that travel in waves

27.2 The Speed of Light Speed of light = extra distance traveled extra time measured = 300,000,000 km / 1000 sec = 300,000 km/sec

27.2 The Speed of Light light year – the distance traveled by light in one year ≈ 9.5 x 1012 km

27.3 Electromagnetic Waves • Waves by which light energy travels • All are radiated by vibrating electrons within an atom

27.3 Electromagnetic Waves

27.7 Polarization Light 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

Reflection – bouncing off • Refraction – penetrating (goes through) and bends

Major parts of a wave: