3. Waves Key Terms Flashcards
Progressive wave
A wave which transfers energy from one place to another, without the transfer of matter
Transverse wave
A wave that oscillates perpendicular to the direction of travel, particles dont move along the direction of the wave
Longitudinal wave
A wave that oscillates parallel to the direction of travel
Amplitude
The maximum displacement of the wave from its undisturbed position
Frequency of wave
The number of oscillations that pass a point in 1 sec. Or the number of complete oscillations in 1 sec.
Time period
The time taken to complete 1 whole oscillation
Wave length of progressive wave
The distance between the same adjacent points on a wave which are in phase with each other
Range of visible wavelengths
400nm - 700mm
Violet - Red
Wave speed
How fast the speed moves due to the frequency and wave length
In phase
The same cycle or period of a wave
0 degree difference
Antiphase
Directly opposite in the same cycle
180 degree difference
The principle of superposition
When two waves on the same plane have the same frequency so can combine their individual displacements to give a bigger total displacement
Coherence
The waves have the same frequency and a constance phase difference which enables them to superpose
Phase difference
The difference between two waves in the same cycle. There can be any degree of phase difference
Standing wave
When two coherent waves meet and superpose. Makes it look like it is stationwary however particles are displacing constantly up and down
Node
The point on a standing wave where there is no displacement, it doesn’t move
Antinode
The point on a standing wave where it has its maximum displacement, it is constantly moving
Harmonic
The amount of fundamentals created on a standing wave
Fundamental mode
Where there is a single loop which equals half the wavelength of the wave.
In phase on a standing wave
There are multiple points on a standing wave that are in phase along each fundamental mode as well as on the opposing wave
Path difference
The difference in distance travelled by two waves, it is expressed by a number or of a fraction of a wave
Phase difference
The difference in positions of 2 points within a cycle of an oscillation
Double slit experiment
wavelength = distance between slits x distance between maximas / distance between light source and maximas
Refraction grating
n x wavelength = distance x sinA
Snells law
n1sin1 = n2sin2
Refractive index
refractive index = speed of light / velocity of particle
Critical angle working
n1sin1 = n2sin90
Critical angle definition
The largest angle of incidence at which refraction can occur
Multipath dispersion
The result of light taking different paths down an optical fibre, this could lead to the merging of data and incorrect readings after the transmission
Monomode fibre
An optical fibre where light can only take 1 path
Also the most efficient cable with the most data transfer
Higher data transfer rates across a much longer distance
Polarisation
When waves are changed to one oscillate in a single plane, only happens with transverse waves
How can light be polarised?
Using a polarisation filter
By reflection
By scattering
what happens to the amount of diffraction when the gaps are small
the diffraction is bigger
when the gaps are bigger what happens to the diffraction
it gives a smaller amount of diffraction
What happens to the wavelength when the wave diffract
It doesnt change
the amount of diffraction ( the angle of spreading) means…
this depends on the wavelength and the size of the gap
what does the angle of incidence equal to
the angle of reflection
Wave speed equation
c or v = f x wavelength
What is two source interference
When two waves from two different sources superpose and form a new wave
What is youngs double slit experiment
When a wave is passed through two slits creating a pattern of maxima and minima on the screen
How was youngs double slit experiment important
It showed that light could act as a wave as well as a particle
Why is using a diffraction grating better than the double slit experiment
It gives a clearer more defined pattern on the screen and it spreads out the pattern more, it is easier to measure between maximas
What is a characteristic of a coherent wave
They are monochromatic
Constance phase difference
What is the refractive index
The ratio of the speed of light in a vaccum to the speed of light in that medium
What happens with total internal reflection
When the light beams reflects off the medium boundary when the angle of incidence is above the critical angle
Why is total interal reflection important
It allows data to travel very fast through optical fibres
