waves Flashcards
oscillations
vibration of a particle w/in a medium
compressions
areas of higher density relative to the surrounding medium in a wave
rarefactions
areas of lower density relative to the surrounding medium in a wave
progressive waves
unbound waves free to move a medium
the transfer of energy between 2 points
standing waves
energy passed back and forth on a wave
wave definition
disturbance in the form of oscillations which transfers energy and not matter
refraction
when the direction of a wave changes due to it speeding up/slowing down as it passes the boundary between media
differences and similarities between a d/s and t/s graph of waves
peak to peak on d/s is wavelength, whereas it is time period on t/s graph
both have the amplitude as the peak/trough
phase difference
amount a wave lags behind another as a proportion of wavelength
φ/2π=x/λ
display of an oscilloscope
y-axis : potential difference of trace
x-axis : timebase (cm/s) - what distance represents a specific time
what happens to the trace of an oscilloscope when timebase increases?
increasing the Timebase will display more cycles of a periodic signal, so the apparent λ decreases
what is held constant during refraction
frequency of wave
means {v α λ}
What is intensity
Radiant power passing through a surface pers unit area
(W/m^2)
I=P/A
What happens to intensity as you go further from a point source
Radiant power spreads out uniformly in all directions (sphere)
Decreases by the surface area of an equal sphere (1/πr^2)
Relation between intensity and amplitude
I α (amplitude)^2
Energy and power related to v^2, and increasing amplitude means v^
Area under α power, so increases by the squared factor
refractive index
how optically dense a material is (c/v)
optical fibres
glass core surrounded by cladding surrounded by air
when light passed into glass, will TIR at the boundaries
light transmitted along fibre w minimal loss
diffraction
when a wave spreads out upon - meeting an obstacle
- passing through a slit
(max when λ = a)
polarisation
most electric fields oscillate in random planes
filters only allow waves of a certain orientation to pass through
(some aerials only detect certain orientations)
polarising filters
polaroid film - vertical lines means only vertically polarised orientations can pass through
metal grille (MO) - horizontal bars only allow for vert. to pass through
polarisation and intensity/Amplitude
I = I(initial) cos^2( θ)
A = A(initial)cos(θ)
(where θ is angle taken from alignment)
coherence
when 2 waves have a constant phase difference (same freq)
achieved by passing one wave through a double slit
