Radio waves emitted from an antenna are picked up by a radar after reflection from an aircraft in 4 x 10\(^{-3}\)S. How far is the aircraft from the antenna? [c = 3 x 10\(^8\)ms\(^{-1}\) ]
A
6.0 x 10\(^2\)km
B
1.2 x 103km
C
3.0 x 103km
D
6.0 x 10 5km
Verified Correct Answer: A.
Physical Principles & Numerical Solution
\(\text{Total time (to aircraft and back)} = 4 \times 10^{-3} \, \text{s} \)
\(\text{Speed of radio waves} = 3 \times 10^8 \, \text{m/s}\)
\(\text{Round-trip distance} = 3 \times 10^8 \times 4 \times 10^{-3}\) = 1.2 \(\times 10^6 \, \text{m}\)
\(\text{Actual distance to aircraft} = \frac{1.2 \times 10^6}{2}\)
= 600,000m = 600km.
Source: Myschool Past Questions Archive (Record #27999)