Y1 Ch 05 Waves Flashcards
Progressive Wave definition
An oscillation or vibration that transfers energy and information not matter.
Frequency definition
The number of cycles or vibrations per second, measured in Hertz
Period definition
Time per cycle, measured in seconds
Amplitude definition
The maximum displacement from the equilibrium line
Wavelength definition
The distance between wake peaks or two equivalent points
Longitudinal wave definition
A wave where the oscillation is parallel to the direction of travel
Transverse wave definition
A wave where the oscillation is perpendicular to the direction of travel
Phase difference definition
the fraction of a wave cycle between two points
Phase difference equation
2pidistance between the two points/wavelength
Polarisation definition
the action of restricting the vibrations of a transverse wave, especially light, wholly or partially to one direction
Polarisation only happens to …..
transverse waves
How can Light be polarised?
- Reflection 2. filters 3. through certain materials
Why is polarisation used?
- to reduce glare 2. to reduce interference
Refraction explanation
as a wave travels from one material to another it will change speed causing it to change direction
Refractive index equation
n = C/Cs
Refractive index definition
The ratio of a wave’s speed in a vacuum to the wave’s speed in the substance
Snells law
N1 * Sinϴ1 = N2 * Sinϴ2
Which has a longer wavelength red light or blue light?
Red light
Total Internal Reflection Definition
when all light is reflected off a boundary of 2 materials if different optical densities
For TIR to occur the angle of incidence must be bigger than the …
Critical angle
How to find the critical angle
Sinϴ = 1/n1
What occurs inside an optic fibre so light can be transferred
Total Internal Reflection
Why is there cladding on an optic fibre
- to increase the surrounding refractive index so only light with a shallower path can be reflected 2. to stop light leaking out when the core is damaged
What must the refractive index of the cladding of an optic fibre be in terms of the refractive index?
Bigger than air but smaller than the core so it can totally internally reflect
Broadening (optic fibres)
The dispersion of pulses - too much broadening causes a reduction in the quality of the signal
Pulse broadening limits …
the frequency of pulses sent down an optic fibre
What do we do to overcome the material absorbing the light energy?
amplify the signal
