just stuff Flashcards
what is modal (multipath) dispersion for fibre optics
If core is wide enough then light travelling along axis then travels the shortest distance than light being repeatedly being TIR.
this stretches data pulses (pulse broadening) which can cause corruption of data.
smaller fibre solves this
what is material (spectral) dispersion on fibre optics
different colours of light have speeds
red fastest and violet slowest
resolved by monochromatic light as this only occurs with white light
how does a fluorescent tube work
low vapour gaseous mercury is in a tube and gets bombarded by electrons form the circuit which causes mercury ions to form.
these ions have higher energy levels so they get excited and when they de-excite they emit a uv photon. this then gets absorbed by the phosphorus coating inside the tube that emits a visible photon.
properties of stationary waves (frequency, amplitude and phase difference)
frequency - particles vibrate at the same frequency except at nodes where no vibrations
amplitude - varies between zero at nodes and maximum at antinodes
phase diff - phase is nπrad, where n is number of nodes between points
properties of progressive waves (frequency, amplitude and phase difference)
frequency - all particles vibrate at the same frequency
amplitude - same for all particles
phase diff - phase is 2πd/λ
what two categories can progressive waves be splint into
transvers - particles oscillate perpendicular to wave direction
longitudinal - particles oscillate in wave direction
