p2:waves - Refraction Flashcards
what happebs to wavefront as they enter a medium
what happens to frequency of light
slow down
stays the same
what happens when light goes from less dense to more dense
light bends towards the normal
what the equations for refraction (3)
sin(I)/sin(r) = n2/n1 = v1/v2
what does n equal in that eqaution
fractional index of material
what does v = in that euqaaiton
speed of ligt in material
whats the refractional indexc of air/vacum
and glass
air/vaccum = 1
glass = 1.6
what happens when light goes down the normal
doesn’t refract
what is the critical angle
It’s the anglr of incidence when the angle of refraction is 90(light refracted along the boundary)
what conditions do we need for the critical angle to work
more dense to less dense
whats the equation for snells law(critical angle)
sin c/sin(90) = n2/n1
what is total interrnal reflection
when the angle of incidence is bigger than the critical angle light is not refracted but reflected
how does a fibre optic cable work
uses a total internal reflection to transfer information
what do we put on fibre optic cables and how does it help
cladding
protects inner fibre form damage
prevents cross talk
what causes material dispersion
white light being hsone inot cables
different wavelengths of light travel at different speeds
name 2 ways of material dispersion
pulse broadening
modal dispersion
how does pulse broadening affect fiber optic cables(2 things)
and how is it caused
signals of light sent in 1s and 0s
spreads pulses which limit the maximum frequency
causes bandwidth availability to decrease
how do we counter pulse broadening(3 things)
use monochromatic light
booster stations
increase amplitude
how does modal dispersion affect fibre optic cables and how is it caused
light taking different paths - causes light to come out at different times
causes pulse broadening
how do we counter modal dispersion(3 things)
using a core
and booster stations
increase amplitude
