Week 3 Progressive Waves

progressive wave

a type of wave that transfers energy without transfering matter (only disturbs), can be longitudinal or transverse waves

what are the two types of waves

mechanical and electromagnetic waves

mechanical waves

needs material or medium to travel through (cannot exist in vacuum), can be transverse or longitudinal (ex. voice [needs air], instrument sounds[needs air], ocean waves [needs water])

electromagnetic waves

do not need medium (can exist in vacuum), always are transverse (ex. radio frequency, visible colors)

what is being disturbed in the air that allows sound to transfer (ex.voice)

pressure in the air

transverse wave

disturbances (or vibrations) are perpendicular to the direction of the wave 

longitudinal wave

disturbance (or vibrations) are parallel to the direction of the wave

wave frequency

the number of waves that pass a fixed point in a given amount of time

what is the SI unit for wave frequency

Hertz (Hz)

radian

SI unit of angular measurement (rad); an arc of a circle with the same length as the radius of that circle, like degrees

what are the 2 features common to all waves

a wave is a travelling disturbance and carries energy from place to place

what is the SI unit for wavelength

meters (m)

what is the equation to find frequency of a wave?

f=1/T, where f=frequency(Hz) and T=period (seconds)

how do you convert radians to degrees and vice versa?

degrees x π/180 = radian

radian x 180/π = degrees

1 cycle/wavelength is equal to how many radians?

2π

what is the equation used to find wave speed?

v=fλ, where v=speed(m/s), f=frequency(Hz), and λ=wavelength(m)

or

v=1/T(λ), where T=period(seconds)

periodic waves

consist of cycles or patterns that are reproduced over and over again by the source

what are the 4 different wave interactions?

reflection, refraction, diffraction, and interference

constructive interference

A crest / trough or condensation / rarefaction of one wave is positioned with the crest / trough or condensation / rarefaction of the other wave (in phase). results in amplitude of the wave thats the sum of the two waves.

deconstructive interference

A crest / condensation of one wave is positioned with the trough / rarefaction of the other wave and vice versa (out of phase). results in the waves canceling each other out leaving only a constant air pressure

reflection wave

when a wave bounces off a surface, staying in its original medium

refraction wave

the change in direction of a wave, such as light or water waves, as it passes from one medium to another, happens because the wave's speed changes at the boundary between the two materials

diffraction wave

the spreading out of waves as they pass through a gap or around an obstacle

water wave

not transverse or longitudinal, instead combines both and move on nearly circular paths

what determines the speed of the wave travelliing

the properties of the medium/material that a wave travels through (tension and mass [mass per unit length])

• except for electromagnetic waves which don’t need a medium

net force

overall, single force that combines all individual forces acting on an object

linear density

mass per unit length m/L

equation to find speed of wave calculating the tension and mass of the material it travels through

v = sqrtF/(m/L), F= tension

sound waves are

mechanical and longitudinal waves

phase difference

measure of difference between two waves; measured in rad/deg

path difference

measure of difference between two waves; measured in meters or a fraction of wavelength