Question

A radar has a power of 1 KW and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance up to which it can detect object located on the surface of the earth is [Radius of earth = $6.4\times {10}^6$m]

• A. 80 km
• B. 16 km
• C. 40 km
• D. 64 km

Answer 1

The correct option is A 80 km

Maximum distance to detect = $\sqrt{(h+R{)}^2-R^2}$
$=\sqrt{2Rh+h^2}$
$=\sqrt{2Rh}$
$=\sqrt{2\times 6.4\times {10}^3\times \frac{1}{2}}$
$=80km$