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 upto which it can detect object located on the surface of the earth (Radius of earth = `6.4 xx 10^(6)` m) is

Options

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

Answer

A

Explanation

`r=R+hR`
`x=sqrt((R+h)^(2)-R^(2))`
`sqrt(h^(2)+2hR)`
`x^(2)=25000+2.500 6.4 100000`
`=25000+(64xx100000000)`
`=10^(4)(640025)`
`x^(2)=10^(4)640000rArr x=8xx10^(4)m=80km`.