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Question
An enemy plane is at a distance of 300 km from a radar. In how much time the radar will be able to detect the plane? Take velocity of radio waves as 3 x 108 ms-1
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Solution
Distance between the plane and the radar, d = 300 km = 300,000 m
Velocity of radio waves, c = 3 x 108 ms-1
Waves from the radar will travel to the plane and then reflect and travel back to the receiver of the radar. Hence, the total distance traveled by the waves is 2d
∴ 2d = c x t
:. `t = (2d)/c`
`:. t = (2 xx 300000)/(3 xx 10^8)`
`:. t = 2 xx 10^(-3) s = 2 ms`
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