CAIE IGCSE Physics Solar System Light Travel Calculations

Practise using light speed with astronomical distances and times, converting kilometres to metres and recognising when a reflected signal travels a round trip.

Exam points

use c = 3.0 × 10^8 m/s with distance = speed × time for Sun–planet or Earth–Moon travel
convert kilometres to metres and handle standard form consistently before substitution
double a one-way Earth–Moon distance for a reflected laser's total path before finding time

[Maximum number: 2]

Jupiter is $7.8 \times 10^{11} \mathrm{~m}$ from the Sun. The speed of light in a vacuum is $3.0 \times 10^{8} \mathrm{~m} / \mathrm{s}$ .

Calculate the time taken for light from the Sun to reach Jupiter.
time =

$2.6 \times 10^{3} \mathrm{~s}$

A2

$v=s / t \mathbf{O R}(t=) s / v \mathbf{O R} 7.8 \times 10^{11} / 3.0 \times 10^{8}$

C1

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6.1.2.4—Time it takes light to travel a question 1