The frequency of a radar is 780 MHz. After getting reflected from an approaching aeroplane, the apparent frequency is more than the actual frequency by 2.6 kHz. The aeroplane has a speed of

Options

A. `0.25 km//s`
B. `0.5 km//s`
C. `1.0 km//s`
D. `2.0 km//s`

Answer

B

Explanation

`upsilon_(r ) = upsilon(1+(2v)/(c ))`
`(upsilon + Delta upsilon)/(upsilon) = 1 + (2 v)/(c )`
`(Delta upsilon)/(upsilon) = (2v)/( c)`
`(2.6 xx 10^(3))/(780 xx 10^(6)) = (2v)/(3 xx 10^(8))`
`v = 500 m//s = 0.5 km//s`