physics Flashcards
what is a transverse wave
particles that oscillate perpendicular to the direction of the wave. There is no horizontal movement.
what is a longitudinal wave
particles that oscillate parallel to the direction of the wave. there is no vertical movement.
what is the peak
the point of maximum positive displacement
what is the trough
the point of maximum negative displacement
what is equilibrium
the point at which particles remain where there is no disturbance
what is the amplitude
the difference between the max and the equalibrium
what is the wavelength
one point of a wave to the identical point on the next wave
what are examples of transverse waves
EM waves
String waves
water waves
S waves
what are examples of longitudinal waves
sound
P waves
what is frequency
the number of waves passing a point per second
what is period
time taken to produce one complete wave
what is the formula for velocity/ wavespeed
V= Fx Lamda wavespeed= frequency x wavelength
what is the EM spectrum in order from shortest wavelength to longest wavelength
gamma ray x ray UV visible light infrared microwave radio
what is the formula for period
1/ frequency
when is there no phase difference
when 2 waves run along the same way at the same point will form one wave (they have the same peak and trough)
when is there a phase difference
the fraction of a complete cycle between 2 points on a wave
what is reflection
when waves hit a barrier/ boundary that they cant pass through, they are reflected.
what is superposition
when 2 or more waves overlap, the displacement at a point is equal to the sum of the individual displacements at the point
what is constructive inference
if both waves the same displacement/ in phase
wave 1+ 2= wave 3
what is destructive inference
when waves are 180 degrees out of phase
if one wave has a positive displacement and the other has a negative
wave 1-2= wave 3
what is a stationary wave
when 2 progressive waves of the same frequency travel in opposite directions, a stationary wave is produced
what is an antinode
when the maximum displacement occurs
what is a node
when no displacement occurs
what is the EM spectrum from the longest wavelength to shortest
radio wave microwave infrared visible light visible light UV x rays gamma rays
why are lasers used as a light source
MONOCHROMATIC- emitted with only one wavelength
COHERENT- all waves are either exactly in phase or display a constant phase difference
COLLIMATED- a narrow, approximately parallel beam
what is refraction
the change of direction a light ray undergoes when it enters a medium with a different optical density
what happens when a light ray enters a medium that is more optically dense
it slows down and bends towards the normal
what happens when a light ray enters a medium that is less optically dense
it speeds up and bents away the normal
what is the formula for incident ray and refracted ray
I1= R2
what is the formula for refractive index
refractive index of a substance (n) = speed of light in the vacuum (c) / speed of light in a substance (v)
OR
sin R (angle of refraction)/ sin I (angle of incidence)
what are optical fibres used for
used to send light signals from one place to another eg cable TV
how do optical fibres work
light from a source is directed into a narrow glass fibre
the ray will undergo a series of total internal reflection each time it works
what are the improvements made on the optical fibre
to wrap the core fibre in a material called cladding
the cladding protects the core from scratches/ moisture that may enable light to leak out
this allows info to be transmitted with a greater degree of security
what other ways do we use optical fibres other than in communication
endoscopes contain 2 bundles of fibres, one is used to light the inside of the person while the other is used to bring back info
what are the types of signal transmissions
analogue signal and digital signal
what is an analogue signal
varies continuously in frequency and amplitude eg speech and FM radio
what is a digital signal
has only 2 states (on and off)
it is transmitted as a series of electrical or optical pulses. eg electrical pluses in cables, infrared pulses in optical fibres
what is an emission spectra
the range of frequencies of light emitted by an element
is produced by an element due to energy level changes of electrons
the electrons lose energy when returning to a lower energy level they emit light of a specific frequency
what is the speed (in instruments)
velocity of a wave on a string= tension in the string/ the mass per unit length of a string
what are the advantages of digital signals
they are less affected by noise and have less energy loss and can travel further
what are microwaves used for
mobile phone networks because their high frequency gives greater bandwidth which allows large amounts of data to be transmitted
why are microwaves good
there is little to no interference because they can be divided into separate channels
what is the quality of a signal affected by
wet weather as microwaves are strongly absorbed by water
what is satellite communication
the signals are high power and are transmitted over long distances
radio waves are reflected by the ionosphere and so it can be used for terrestrial communication
what are infrared communications
used in low power devices such as remote controls
operates over a short distance and in line of sight
doesnt work well in bright sunlight
