Waves

Wave: A propagating disturbance (transfer of energy without transfer of matter)
Particles move back and forth while the wave of energy keeps moving in one direction

Longitudinal Waves: Particle motion is parallel to wave energy motion

Transverse Waves: Particle motion is perpendicular to wave energy motion

Frequency - how many waves pass by per second

  • Higher frequency waves have more energy
  • measured in Hz
    Wavelength and Frequency are inversely proportional

Mechanical Waves: Need a medium (air, water, slinky, etc)

  • Transverse or longitudinal waves

Electromagnetic Waves: Don’t need a medium (can travel through a vacuum like space)

  • Transverse waves
    Wave velocity: how far one wave can travel in a certain amount of time

period of the wave: How long it takes for one wave to pass by the roots (T)

frequency of the wave: How many waves pass by the roots per second (F)

Period and Frequency are inversely proportional

Radio waves travel at the speed of light

Sound is a mechanical wave and is a longitudinal wave

Compression - pulse of compressed air

Rarefaction - Areas of low pressure air between compressions

Frequency of a sound wave controls the pitch

Amplitude of a sound wave controls its loudness

Doppler affect: Sound waves travel in all directions from the source but if the source is moving toward you it would be higher pitch than moving away from you

Subsonic - slower than the speed of sound

Mach 1 - at the speed of sound

Supersonic - faster than the speed of sound

Waves don’t collide with each other they pass through each other

Principal of Superposition - The amplitude of an observed wave equals the sum of the amplitudes of all overlapping waves

Constructive Interference: Crests match up with crests and troughs with troughs to increase the amplitude of the observed wave.

Destructive Interference: Crests match with troughs to decrease the amplitude of the observed wave.

Beats: When two waves differ slightly in frequency, they alternate between constructively and destructively interfering

When waves reflect they interfere with each other

Fixed End: Destructive interference and inverted wave

Loose end: constructive interference and non-inverted wave

Standing Waves: An interference pattern caused when a wave reflects and interferes with itself
And only Works on lengths that are multiples of 1/2 a wavelength

Woodwind instruments use standing waves of air within their hollow bodies to make particular notes

What's the biggest standing wave possible on a string instrument? Biggest standing wave possible is half of a wavelength for strings

Fundamental frequency - the smallest frequency a standing wave can have in a string instrument

All possible frequencies are whole number multiples of the fundamental frequency (harmonics/overtones) in a string instrument

Open ended instruments: Ends of possible standing waves are antinodes instead of nodes andFundamental frequency still occurs with half a wave and Harmonic frequencies are whole number multiples of fundamental frequency

Pipes Open at ONE END ONLY: Node at closed end; Antinode at open end, Fundamental frequency occurs with 1/4 of a wavelength, Only odd harmonics (ends at an antinode)