Q. 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 $500m$. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth $= 6.4 \times 10^{6}m$) is
A) 80 $km$
B) 16 $km$
C) 40 $km$
D) $64\ km$
Explanation
(a) $d = \sqrt{2hR} = \sqrt{2 \times 500 \times 6.4 \times 10^{6}}\ m$
$= 80,000m = 80\ km$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.