A standing wave is produced when a wave that is traveling is reflected back upon itself. There are two main parts to a standing wave:

Antinodes – Areas of MAXIMUM AMPLITUDE

Nodes – Areas of ZERO AMPLITUDE.

Sound Waves are a common type of standing wave as they are caused by RESONANCE.

Resonance – when a FORCED vibration matches an object’s natural frequency thus producing vibration, sound, or even damage.

Example - shattering a wine glass by hitting a musical note that is on the same frequency as the natural frequency of the glass.

Example – Tacoma bridge collapse

Tacoma Narrows Bridge Collapse

http://www.youtube.com/watch?v=3mclp9QmCGs

Electromagnetic wave - capable of transmitting its energy through a vacuum (or empty space). ◦ Produced by the vibration of charged particles. ◦ Ex. All light waves

Mechanical wave - not capable of transmitting its energy through a vacuum.◦ Require a medium in order to transport their energy

from one location to another.◦ Ex. Sound, slinky, water, standing waves.

• Longitudinal waves produced by a vibration• Changes in pressure (high to low)

• Molecules in the air vibrate about some average position creating the compressions and rarefactions.

•a wavelength is the distance from a compression to the next compression (or from a rarefaction to the next rarefaction)

Wavelength of a wave tells you the frequency

Frequency is measured in Hertz (Hz)

◦ Frequency is the pitch of a sound High pitch = high frequency/ Low pitch = low frequency

Doubling the frequency = octave

High frequencies are high sounds (whistle) with high pitches

Low frequencies are low sounds (tuba) with low pitches.

Who has higher frequencies, women or men?

Amplitude of a wave, tells you the loudness

Measure in decibels (dB) Increase of 20 dB = twice the volume

Loud Soft

Sound Loudness (dbs) Hearing Damage

Average Home 40-50

Loud Music 90-100 After long exposure

Rock Concert 115-120 Progressive

Jet Engine 120-170 Pain

Below 20 Hz – Infrasonic◦ Elephants communication,

Average human hearing (audible sound) ranges from 20 Hz to 20,000 Hz

Above 20,000 Hz – Ultrasonic ◦ Ultasounds

Most sounds are transmitted through air◦ In general, sounds are transmitted easily in solids,

then liquids, and slowest is air (gases.)

◦ Ex. Hold your ear to the ground to hear horses off at a distance.

Speed of Sound in Various Media

Medium Speed of Sound (m/s)

Air (0°C) 331

Air (20°C) 343

Helium (0°C) 972

Water (25°C) 1493

Seawater (25°C) 1533

Copper (25°C) 3560

Iron (25°C) 5130

Two speakers (green dots) generating sound. Listeners at the red points will hear the sound better than listeners at the blue points.

Why?Thus, constructive interference occurs wherever a thick

line meets a thick line (or thin line meets a thin line) this type of interference results in antinodes (red dots).

Blue dots are the nodes, places of destructive interference.

phenomenon observed whenever the source of waves is moving with respect to an observer.

observed to occur with all types of waves - water waves, sound waves, and light waves.

Ex. A police car traveling towards you on the highway. As the police car approached with its siren blasting, the pitch of the siren sound was high; and then suddenly after the car passed by, the pitch of the siren sound was low. 

To calculate the speed of sound, use the equation:speed = distance/time s = d/tspeed = frequency)(wavelength) v = fλ

Speed depends on the medium. Will be given a chart of the various speeds

in different mediums.

Sound waves with a constant frequency of 250Hz are traveling through air at 0 C. What is the wavelength of the sound waves?

Speed of Sound in Various Media

Medium Speed of Sound (m/s)

Air (0°C) 331

Air (20°C) 343

Helium (0°C) 972

Water (25°C) 1493

Seawater (25°C) 1533

Copper (25°C) 3560

Iron (25°C) 5130