# The deer gets startled and runs. When it stops, the laser range finder indicates that it is 183m away. How long does it take the laser beam to reach the deer? How long does it take the laser beam to return to the range finder?

##### 1 Answer
Jun 12, 2016

(a) $6.1 \times {10}^{-} 7 s$
(b) $1.22 \times {10}^{-} 6 s$

#### Explanation:

For a laser range finder the distance $D$ between point $A \mathmr{and} B$ is given by

$D = \frac{c t}{2}$
where $c$ is the speed of light in the atmosphere $= 3 \times {10}^{8} m {s}^{-} 1$ and $t$ is the time taken by the laser for the round-trip between the points $A$ and $B$.
Given $D = 183 m$
Time taken by the laser beam to reach the deer$= \text{Distance"/"Speed}$
$= \frac{183}{3 \times {10}^{8}}$
$= 6.1 \times {10}^{-} 7 s$

Time taken by the laser beam to return to the range finder$= 2 \times 6.1 \times {10}^{-} 7$
$= 1.22 \times {10}^{-} 6 s$