Polarisation, refraction, and optical fibres Exam Questions and Answers Latest Update already Passed
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Course
Fibre Optic
Institution
Fibre Optic
Polarisation, refraction, and optical fibres Exam Questions and Answers Latest Update already Passed
What type of waves can be polarised? - Answers Only transverse waves
When light passes through a polarising filter, how does its intensity change? - Answers It halves
When light passes through t...
Polarisation, refraction, and optical fibres Exam Questions and Answers Latest Update already Passed
What type of waves can be polarised? - Answers Only transverse waves
When light passes through a polarising filter, how does its intensity change? - Answers It halves
When light passes through two polarising filters, with their transmission axes perpendicular, how does
its intensity change? - Answers No light gets through
State 2 uses of polarisation. - Answers In polaroid sunglasses & cameras to reduce glare. For the
alignment of TV aerials
What is unchanged when light moves from one material to another? - Answers Frequency (wavelength,
speed and amplitude all change)
If the refractive index is higher, how is the speed and wavelength of light different? - Answers The speed
is lower and the wavelength is shorter.
When light moves from a material with high n to one with low n, how does its direction change? -
Answers It bends away from the normal (the angle of refraction is greater than the angle of incidence)
What are the 2 conditions for total internal reflection to occur? - Answers the ray starts in the higher
refractive index material, and the angle of incidence is larger than the critical angle.
What are the 3 parts of an optic fibre? - Answers Core - central part, high refractive index (n), Cladding -
low n, Sheath - outermost layer, just for protection
What is the purpose of the cladding? - Answers 1) To protect outer surface of core from stretching or
breakage and prevent loss of signal from scratches
2) Provide a lower refractive index so TIR happens
3) Prevent crossover / cross-talk in a bundle of fibres - ensure data security
What is the purpose of the sheath? - Answers 1) Protects fibre & cladding Provides strength
2) Prevents loss of signal from scratches
3) Prevent crosstalk
What 2 processes cause signal loss? - Answers 1) Dispersion - pulse broadening, pulses get wider,
merging into each other
2) Attenuation - absorption and leakage of light reduce the amplitude of signals / cause power loss
What is material dispersion (& what's another name for it)? - Answers (Also called chromatic dispersion)
Violet/blue light travels more slowly than red light in glass, Red light reaches the end before blue. This
leads to material pulse broadening
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