Calculating the Time it Takes Light to Travel a Given Distance

The sun is 1.50 × 10⁸ km from Earth. How long does it take light to travel from the sun to Earth in minutes and seconds?

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Strategy
Identify knowns.

$\begin{array}{l} Distance = 1 .50 \times 10^{8} km \\ Speed = 3 .00 \times 10^{8} km \end{array}$
10.1

Identify unknowns.

Time

Find the equation that relates knowns and unknowns.

$v = \frac{d}{t}; t = \frac{d}{v}$
10.2

Be sure to use consistent units.
Solution
$\begin{array}{l} t = \frac{d}{v} = \frac{(1.50 \times 10^{8} k m) \times \frac{10^{3} m}{km}}{3.00 \times 10^{8} \frac{m}{s}} = 5.00 \times 10^{2} s \\ 500 s = 8 min and 20 s \end{array}$

0 of 2 steps open

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