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

given,

Echo time = t = 1000 s

speed = ?

`v = (d)/(t)`

a) speed of electromagnetic wave

`c = (d)/(t)`

wave travels Venus two time

`c = (2d)/(t)`

`d = (ct)/(2)`

`d = (3 * 10^8* 1000)/(2)`

d = 1.5 x 10¹¹ m

b) now, echo time

`c = (2d)/(t)`

`t = (2d)/(c)`

`t = (2* 75)/(3 * 10^8)`

t = 5 x 10⁻⁷ s