About 100 days ago, the airplane MH370 was lost.
In locating the airplane, one of the ways that Inmarsat used was the Doppler effect. If there is an object emitting a signal e.g. sound, the frequency of the signal as detected by someone elsewhere, depends on the speed and direction at which the object is traveling.
After contact with the airplane was lost, the plane’s only form of communication was electromagnetic ‘pings’ indicating that the plane was still operational. The frequency of each ‘ping’ would change as the plane moved with respect to satellite used for detection. As we know the original frequency at which the plane emitted the ‘pings’, we could determine the change in frequency and thus calculate the velocity of the plane with respect to the satellite.
While we can get an idea of the plane’s direction of travel from the Doppler effect, it is still difficult to know the exact position of the plane. The concept of Doppler effect is not officially tested in the Cambridge exams but if students would like to know more, feel free to raise it up during our JC Physics tuition classes. It is however tested in the Physics Olympiad program.