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Question 18M.3.SL.TZ2.10b.iii

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Date May 2018 Marks available [Maximum mark: 2] Reference code 18M.3.SL.TZ2.10b.iii
Level SL Paper 3 Time zone TZ2
Command term Discuss Question number b.iii Adapted from N/A
b.iii.
[Maximum mark: 2]
18M.3.SL.TZ2.10b.iii

An optic fibre of length 185 km has an attenuation of 0.200 dB km–1. The input power to the cable is 400.0 μW. The output power from the cable must not fall below 2.0 μW.

(b.iii)

The graph shows the variation with wavelength of the refractive index of the glass from which the optic fibre is made.

                                           M18/4/PHYSI/SP3/ENG/TZ2/10.b.ii

Two light rays enter the fibre at the same instant along the axes. Ray A has a wavelength of λA and ray B has a wavelength of λB. Discuss the effect that the difference in wavelength has on the rays as they pass along the fibre.

[2]

Markscheme

mention of material dispersion

mention that rays become separated in time

OR

mention that ray A travels slower/arrives later than ray B

[2 marks]

Syllabus sections