Solution

Problem

$14.1.1.$ A radio signal reflected from an airplane returned to the radar after $10^{-4}$ seconds. How far was the airplane from the radar at the moment the signal was reflected?

Solution

If the airplane is at a distance $l$ from the radar, the radio signal travels this distance twice – first from the radar to the airplane, and then back. The speed of the radio signal is equal to the speed of light.

$$2l = c \cdot t$$

$$l = \frac{c \cdot t}{2}$$

Substituting the values, we get:
$l = 15$ km.