refraction

Question 1

on why TIR would not occur

Answer 1

(TIR) only when ray travels from higher n to lower n

Question 2

advantages smaller diameter core

Answer 2

• improved data transfer / information / data / signal carried quicker
• less multipath dispersion (smearing / overlap of pulses)
-TIR more likely to occur

Question 3

another advnategs smaller diameter core (2)

Answer 3

to reduce multipath or multimode dispersion (1)

(which would cause) light travelling at different angles to arrive at different times/pulse broadening

Question 4

another advantage smaller diameter core (2)

Answer 4

to prevent light/data/signal loss (from core or fibre) (1)

data to be less secure (1)

Question 5

1 marker on why light ray enters cladding

Answer 5

angle incidence < critical angle

Question 6

why optical fibres need cladding

Answer 6

keeps signals secure (1)
maintains quality/reduces pulse broadening/smearing (owtte) (1)
it keeps (most) light rays in (the core due to total internal reflection at the cladding-core boundary) (1)
it prevents scratching of the core (1)

Question 7

angle incidence equal to critical angle

Answer 7

When the angle of incidence is equal to the critical angle, the angle of refraction is equal to 90

Question 8

why amplitude of pulse lower at end of fibre

Answer 8

• multi-path (modal) dispersion /different rays/modes propagating at different angles take longer time to travel same distance along fibre as axial rays
• absorption or energy loss w/ fibre

Question 9

1 Diff laser light to filament

Answer 9

polarised

Question 10

why glass cladding improve security and why important

Answer 10

light does not enter the cladding - so cannot pass across from one fibre to a neighbouring fibre (1)

personal data must be transmitted along fibres from which there is no danger of leakage of light resulting in a breach of security (1)