1.

A radar operates at wavelength 50.0 cm. If the bbeat frequency between the transmitted signal and the signla reflected from aircraft (Deltav) is 1 kHz, then velocity of the aircraft will be :

Answer»

`800 (km)/(H)`
`900 (km)/(h)`
`1000 (km)/(h)`
`1032 (km)/(h)`

Solution :Source at rest, observer moving towards source
`v. = (C + a)/(c) v`
when surce moves towards observer at rest
`v.. = (c)/(c-a) v. = (c + a)/(c - a) v = [1 + (a)/(c)]/(1 - a/c) v`
`= (1 + (a)/(c))(1 - (a)/(c))^(-1) v`
`therefore Deltav = v.. - v = (2av)/(c) = (2A)/(lambda)`
`therefore a = lambda .(Deltav)/(2) = 250 m s^(-1) = 900(km)/(h)`.


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