Total Internal Reflection Flashcards
State what is meant by monochromatic light.
electromagnetic waves with one frequency & one wavelength
State what is meant by multichromatic light.
electromagnetic waves with multiple different frequencies & wavelengths
State what is meant by the critical angle.
the angle of incidence when the angle of refraction is 90 degrees
State the equation for the critical angle.
sinθ꜀ = n₂ / n₁
When will an electromagnetic wave refract along the boundary?
when it is passing from a higher refractive index to a lower refractive index
What are the two conditions needed for TIR?
n₁ > n₂
θᵢ > θ꜀
State which of the two has a higher refractive index, core or cladding.
core
State what a optical fibre is made of.
core & cladding
State the purpose of the core of an optical fibre.
to provide a medium for total internal reflection
State the purpose of the cladding of an optical fibre.
- protect the core
- enable TIR
- prevent info from leaving the core
What type of media are the core and cladding made of?
transparent media
State the two problems faced in optical fibres.
- pulse absorption
- pulse broadening
What is pulse absorption?
- pulse reaches end of optical fibre with much lower amplitude than it began with
- results in loss of info
State three solutions to modal dispersion
- short distances
- increase refractive index of cladding
- monomode fibre
Explain how changing the refractive index of the cladding can reduce the amount of modal dispersion.
- increase refractive index of cladding
- this gives a larger critical angle
- range of successful angles of incidence decreases
- smaller range of possible paths
(can’t exceed refractive index of core, otherwise no TIR)
