waves Flashcards
what is a wave
A wave is the oscillation of particles or fields
define a cycle
time period
frequency
phase
phase differrence
one complete vibration of a wave
time taken for a whole cycle to complete or pass a given point
number of cycles per second passing a given point
a measurement of the position of a certain point along the wave cycle
the amount one wave lags behind another(Phase difference may be measured as angles (radians and degrees) or as fractions of a cycle.)
how may a part of a wave appear not to be moving
a stationary wave is formed
by either interference or superposition
creating a node, which appears stationary
and waves always cancel eachother out at a node
what is polarisation
The restriction of the vibration of a wave so that it can only oscillate in a single plane
why cant longitudinal waves be polarised
since theycannot be polarised to a single plane since they have vibrations parallel….
what would you observe as a wave is passed through a polarising filter
variation in intensity between max and min
what are polarising filters used for
polarised sunglasses to reduce glare
camera - to reduce glare/ enhance the image
3d glasses to enhance a viewing experience
Equation for critical angle
refractive index of air/ refractive index of solid
refractive index formula
angle incidence/ angle of refraction
parts of a fibre optic cable
core and cladding
fibre optic used in data transmission/broadband - since it gives improved transmission of data or higher speed internet
why is the core of a fibre optic cable made to be narrow as possible
so that multipath/multimode dispersion is reduced - light at diff angles arrive at diff times- loss of data from fibre
what conditions have to be there for Total internal reflection to take place
the ray must be travelling from a higher refractive index to a lower refractive index
why is there cladding in a fibre optic
to protect the core from scratches or breakage
to increase the critical angle
to increase rate of data transfer#
keeps data secure
what is a coherent light
waves with a constant phase difference, same frequency, and same wavelength, a double slit is a coherent source of light
how does wavelength effect a fringe from a double slit experiment
greater the wavelength, the greater the fringe separation- the maxima are further apart from eachother
how would the slit being narrower effect the fringes
greater/wider fringe separation and lower intensity
how is there a formation of waves on a screen from a double slit
fringes formed by interference
where light from the source superpose(overlap)
the red/bright fringes are formed by constructive interference(reinforcement)
the dark fringes is where the 2 waves cancel out by destructive interference
light from the 2 slit are coherent
in the equation of fringe separation (w=Dλ/s)
what does each symbol stand for
W= fringe separation
D= distance from slits to screen
s = distance Between slits
λ = wavelength
formation of fringes from a white light are described as
a bright white central fringe
side fringes to it are continuous spectra
the bright fringes are blue on side nearest to centre
conditions for constructive interference
0 degree phase diff between the 2 waves that interact
path differrence is a multiple of lambda
conditions for destructive interference
phase difference of 180 degrees ( in antiphase)
path differrence (n+1/2)λ
first harmonic to third harmonic
frequency 1st : 10hz
frequency 2nd : 20 hz
frequency 3rd : 30 hz
length- λ/2 λ 3/2λ
phase diff between 2 adjacent nodes is λ/2
conditions for a stationary wave
same freq and amplitude
move in opposite directions
properties of a stationary wave
no energy transferred
nodes are points where the waves have no displacement
antinodes is points at the waves max displacement
what is material dispersion
waves of different wavelengths travel at slightly differrent speeds through an optical fibre and therefore reach the end at diff times
what is modal dispersion
waves enter the optical fibre at different angles, this means the distance each beam has to travel is slightly different, this means they reach the end at diff times - causing pulse broadening
with path diference, what determines whether a wave is interfering destructively or constructively with a wave
If the path difference is a multiple of λ ( nλ ) then its constructive interference
If the path difference is a n/2, 3n/2 ect gives destructive interference
