Unit 3 Waves Flashcards
What do waves do?
transfer energy from 1 place to another by oscillating, and we can interpret that energy into meaningful information. however they cannot transfer matter.
What is a distance/displacement graph?
a graph that shows how far the wave has travelled from the starting point compared to how far from the equilibrium the wave has oscillated
What is amplitude?
the maximum displacement
What is wavelength?
the distance of one entire oscillation
What are some ways to measure wavelenth?
crest to crest, trough to trough, equilibrium to equilibrium
What is a displacement/time graph?
a graph that shows how far from the equilibrium point the wave has oscillated in a certain amount of time
the wavelength is the time period of one full oscillation
What is frequency?
number of complete oscillations per second
What is the unit for frequency?
Hz, hertz
What is the formula for frequency?
frequency (hz) = 1/time (s)
What is the wavespeed?
total distance travelled by the wave in a given amount of time
What is the formula for wavespeed?
wavespeed (m/s) = frequency (Hz) x wavelength (m)
What are transverse waves?
waves that oscillate perpendicular to the direction of energy transfer
most waves are transverse
What direction to transverse waves follow?
travel left to right, up and down oscillations
What are some examples of transverse waves?
electromagnetic waves, light waves, radio waves, ripples
What are longitudinal waves?
waves that oscillated parallel to the direction of energy transfer
some regions are more spread out and some are compressed because the waves vibrate back and forth and different speeds
What are some examples of longitudinal waves?
sound waves, seismic p waves
What are electromagnetic waves?
transverse waves that transfer energy from the source of the waves to the absorber
What speed are electromagnetic waves at in a vaccum?
the all travel at the same speed (3x10^8)
Describe the motion of electromagnetic waves through different mediums
when they go through different mediums they travel at different speeds which leads to refraction. the wavelengths and frequencies differentiate the waves
What is the relation between wavelength and frequency?
inversely related
What happens when an electromagnetic comes into contact with something?
reflected, absorbed or transmitted (or a combination of all)
What are sound waves?
longitudinal waves that can be reflected, refracted and absorbed. they are vibrations that pass through the molecules of a medium and cause collisions that transmit the sound to the other side. the frequency will never change but speeds can.
What happens when a wave comes into contact with a boundary?
a boundary is a surface
it can be absorbed, transmitted (refraction), and reflected
depends based on wavelength and properties of two materials
What is the main rule for ray diagrams?
angle of incidence = angle of reflection
What is the normal?
in a ray diagram the normal is a line that is perpendicular to the boundary
What are the types of reflection?
specular reflection, diffuse/scattered reflection
What is specular reflection?
when the boundary is flat so the all incoming light rays will be reflected in the same direction. it gives a clear image.
What is diffuse/scattered reflection?
when the boundary is bumpy so the normal is all in different directions making the light reflect in different directions.
What is refraction?
when waves change direction as they pass from one medium to another
Why do waves travel at different speeds in different mediums?
because they have different densities. high density makes a slower wave and vice versa
When will a wave be refracted?
when it hits the boundary at an angle it will be reflected and it’s direction will change. if it hit it perpendicular it will move straight.
Which way towards the normal will the wave move depending on the density of the medium they’re passing through?
if its passing into a more dense medium it will bend towards normal
if its passing into a less dense medium it will bend away from normal
Does the frequency ever change?
no it remains constant
What is the relationship between wavespeed and wavelength?
directly proportional
Does wavelength vary refraction amount?
yes, different wavelengths are refracted by different amounts
What happens in the white light triangular experiment?
when white light enters a triangular prism all the colours will bend to different degrees and spread out
What is the refractive index?
a measure of the speed of light as it passes through that material compared to the speed of light as it passes through a vacuum
How does the refractive index of a material affect the wavespeed?
light travels through materials with a higher refractive index slower
light travels through materials with lower refractive index faster
What is a vaccum?
the medium with the lowest refractive index (refractive=1) light travels faster in this medium
How to find refractive index of a material?
speed of light in vaccum/speed of light in material
n=c/v
What is Snell’s Law?
n = sin i/sin r
i = angle of incidence
r = angle of refraction
n = refractive index
What is total internal reflection?
if angle of incidence is greater than critical angle no refraction occurs and all light is reflected back into denser medium
What happens when light travels from a more dense to less dense medium?
it speeds up and is refracted away from normal
What is the criteria for total internal reflection?
the rays of light must travel from more dense to less dense medium and angle of incidence must be greater than the critical angle
What happens when the angle of incidence is less than the critical angle?
light ray refracted away from normal
What happens when the angle of incidence is equal to the critical angle?
the light ray is refracted 90° to the normal and the ray travels along the surface of the denser medium
What is the equation for the critical angle?
sin(c) = 1/n
c = critical angle
n = refractive index
What does the exact value of the critical angle depend on?
the refractive index of that specific material
