# Day 1 - Wave Characteristics

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Day 1 - Wave Characteristics
Waves and Sound Day 1 - Wave Characteristics

What are waves? Def. - Disturbances that carry energy from place to place, through matter or space.

Waves are made when you speak And heard when you listen
Waves can travel through space Most waves begin with a vibration Waves are made when you speak And heard when you listen Waves can make the earth move and shake And make the light you see

is the material in which a wave moves
gas Liquid A medium can be a: Music from your radio to your ear How dolphins communicate solid wood of a guitar Medium is the material in which a wave moves

The medium can move in two ways:
Motion of Medium Energy moves through the medium. The medium just vibrates back and forth and doesn’t move with the wave. The medium can move in two ways: 1. Transverse waves 2. Longitudinal waves

Medium moves at right angles to the direction of the wave.
Transverse waves Medium moves at right angles to the direction of the wave. Ex) football stadium wave A) Crest: highest point B) Trough: lowest point

Rest position or Parts of a Transverse Wave Crest Amplitude Trough
Wavelength Amplitude Rest position or Trough

A) Compressions: where the molecules are crowded together
Longitudinal waves Medium moves parallel to the direction of the wave Ex. – a “slinky” or metal spring Made up of: A) Compressions: where the molecules are crowded together B) Rarefactions: where the molecules spread apart.

Compression Compression Rarefaction Parts of a Longitudinal wave
Wavelength: Compression Compression + Rarefaction Compression Rarefaction

Wave characteristics Wavelength: the distance between a point on one wave and the identical point on the next. (crest to crest, compression to compression) Unit: meter Symbol: l Lambda

Directly related to the amount of energy carried.
Amplitude Def: the distance from the crest or trough of a wave to the rest position. Directly related to the amount of energy carried.

If 3 waves went by in 1 second… You have 3 waves per Second
Frequency: the # of waves that pass one place each second. Unit: hertz (Hz) If 3 waves went by in 1 second… You have 3 waves per Second Frequency would be 3 Hz

Waves and Sound Day 2 - Calculating Speed of a Wave

The Speed of a Wave is affected by two things...
1.) Type of Medium 2.)Temperature

Why?

Waves travel fastest in solids, slowest in gases.
Type of medium Solid Liquid Gas 3 Waves travel fastest in solids, slowest in gases.

Do molecules move faster or slower as temperature increases?
So would sound travel faster or slower as temperature increases?

Air = 340 m/s water= 1440 m/s steel = 5000 m/s
Speed of sound Sound waves travel slower than light waves Speed varies, depending on the medium Air = 340 m/s water= 1440 m/s steel = 5000 m/s

V= l x f Velocity (m/s) Frequency (Hz) Greek ‘lambda’
Wave speed Equation Velocity (m/s) Frequency (Hz) V= l x f Greek ‘lambda’ Stands for wavelength (m)

Sample wave problems... A tuning fork has a frequency of 280 Hz and the wavelength of the sound produced is 1.5 meters. Calculate the velocity of the wave. Step 1 Step 2 Step 3 Step 4

Sample wave problems... A wave is moving toward shore with a velocity of 5 m/s. If its frequency is 2.5 Hz, what is its wavelength? Step 1 Step 2 Step 3 Step 4

Sample wave problems... Earthquakes can produce three types of waves. A typical “S” wave travels 5000m/s. Its wavelength is about 417m. What is the frequency? Step 1 Step 2 Step 3 Step 4

Waves and Sound Day 3 - Wave Behaviors

Wave Behaviors Interference 3. Refraction Reflection 4. Diffraction
Four types Interference 3. Refraction Reflection 4. Diffraction

Reflection Bouncing back of a wave after it strikes a barrier that does not absorb the energy. An echo is a Sound wave that has been reflected Barrier

Angle of incidence = angle of reflection
Law of Reflection Angle of incidence = angle of reflection

Used to locate underwater objects and distances.
sonar Used to locate underwater objects and distances. ***Reflection**

Sonograms: Ultrasonic waves (about 20,000 Hz) used to create images of fetuses in the womb
Regular sonogram 3D sonogram

Refraction: Bending of waves due to a change in speed (this occurs because the wave changes mediums)

Refraction Why does the pencil appear to be broken when placed in a beaker of water??

Diffraction: Bending of waves around the edge of a barrier

There are two types of Wave interference: 1. Constructive Interference
Def. - Interference is the result of two or more waves passing through a medium at the same time. There are two types of Wave interference: 1. Constructive Interference 2. Destructive Interference

Wave interference Constructive Interference: two crests meet and make a wave with a bigger amplitude.

Wave interference Destructive Interference: one crest & one trough meet and make a wave with a smaller amplitude..

Waves and Sound Day 4 - Intro to Sound

Def. – the study of the science of sound
Acoustics Def. – the study of the science of sound Knowledge of acoustics is important to people who design libraries, concert halls, auditoriums, etc.

(cannot travel in a vacuum)
Sound Longitudinal Wave an oscilloscope is used to convert sound waves into transverse waves, so that we can study them Requires a medium (cannot travel in a vacuum)

High frequency = High pitch
The highness or lowness of sound. Depends on the frequency of sound waves. High frequency = High pitch Low frequency = Low pitch

Ultrasonic Sound: above 20,000Hz
Human Ear 20Hz Hz Infrasonic: below 20 Hz Ultrasonic Sound: above 20,000Hz

Sonograms: Ultrasonic waves (about 20,000 Hz) used to create images of fetuses in the womb
Regular sonogram D sonogram

Supersonic: faster than the speed of sound.
Transonic: where only some parts of the air around an object (such as the ends of rotor blades) reach supersonic speeds (typically somewhere between Mach 0.8 and Mach 1.2). A US Navy F/A-18E/F Super Hornet in Transonic Flight

An equal mixture of all frequencies of sound
White Noise An equal mixture of all frequencies of sound

Change in pitch due to motion.
Doppler effect Change in pitch due to motion.

*moving towards increases the pitch *moving away decreases the pitch
Doppler effect *moving towards increases the pitch *moving away decreases the pitch zoom New word for the day: Dopeler Effect (n) The tendency of stupid ideas to seem smarter when they come at you rapidly.

Large Amplitude = Loud sound Small Amplitude = Soft sound
Intensity Amount of energy measured in decibels (dB) Depends on the amplitude of sound waves. Large Amplitude = Loud sound Small Amplitude = Soft sound

Measurement of loudness
Decibels Near total silence - 0 dB A whisper - 15 dB Normal conversation - 60 dB Lawnmower - 90 dB Threshold of pain dB A rock concert or a jet engine dB Gunshot, firecracker dB

A sound tube designed to decrease roadway noise
Noise Pollution Displeasing sounds that disrupt the activity or happiness of human or animal life. Causes: Damage to the ear Stress Hearing Loss A sound tube designed to decrease roadway noise