Question

Radar is used to determine distances to various objects by measuring the round-trip time for an echo from the object. (a) How far away is the planet Venus if the echo time is 1000 s? (b) What is the echo time for a car 75.0 m from a Highway Police radar unit?

Answer 1

Answer

given,

Echo time = t = 1000 s

speed = ?

$v = \dfrac{d}{t}$

a) speed of electromagnetic wave

$c = \dfrac{d}{t}$

wave travels Venus two time

$c = \dfrac{2d}{t}$

$d = \dfrac{ct}{2}$

$d = \dfrac{3 \times 10^8\times 1000}{2}$

d = 1.5 x 10¹¹ m

b) now, echo time

    $c = \dfrac{2d}{t}$

    $t = \dfrac{2d}{c}$

    $t = \dfrac{2\times 75}{3 \times 10^8}$

          t = 5 x 10⁻⁷ s