After 1 second, the aircraft is now at position A1 and under these conditions the next 60 hertz radio wave emitted is between the radar and point A1. Note that this distance is only 720 m (1,080 - 360). The 60 hertz which have a wavelength of just 12 m (720 divided by 60) are distributed across it. Using the formula f=vλ, we can calculate that the new frequency will be 90 Hz. The original frequency of 60 Hz is now an apparent frequency of 90 Hz. This change in the Doppler effect is directly proportional to the speed of the approaching aircraft. The higher the speed of the incoming aircraft, the more waves will accumulate in the space between the radar and the aircraft. This allows us to make detailed calculations to approximate the speed of the aircraft. Therefore, the use of the Doppler effect is an important factor in the effective operation of a radar system. Characteristics of an efficient SONAR