DP Physics (last assessment 2024)

Question 19N.3.SL.TZ0.b(ii)

Date	November 2019	Marks available	[Maximum mark: 2]	Reference code	19N.3.SL.TZ0.b(ii)
Level	SL	Paper	3	Time zone	TZ0
Command term	Determine	Question number	b(ii)	Adapted from	N/A

b(ii).

[Maximum mark: 2]

19N.3.SL.TZ0.b(ii)

Communication signals are transmitted over long distances through optic fibres.

A signal is transmitted along an optic fibre with attenuation per unit length of 0.40 dB km^–1. The signal must be amplified when the power of the signal has fallen to 0.02 % of the input power.

Determine the distance at which the signal must be amplified.

[2]

Markscheme

attenuation = $10 \log (2 \times 10^{- 4}) = - 37$ «dB» ✔
amplification required after $\frac{37}{0.4} = 92$ or 93 «km» ✔
NOTE: Allow ECF from mp1 for wrong dB value.(eg: 42 km if % symbol ignored).

Syllabus sections

Option C: Imaging

Option C: Imaging » Option C: Imaging (Core topics) » C.3 – Fibre optics

Option C: Imaging » Option C: Imaging (Core topics)

Question 19N.3.SL.TZ0.b(ii)

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