Two electric trains run at the same speed of 72 km/h along the same track and in the same direction with a separation of 2.4 km between them. The two trains simultaneously sound brief whistles. A person is situated at a perpendicular distance of 500 m from the track and �s equidistant from the two trains at the instant of the whistling. If both the whistles were at 500 Hz and the speed of sound in air is 340 m/s, find the frequencies heard by the person.

As the person is not sitting on the direct path of the sound wave, the person will hear a fraction of sound depending on the angle shown in the diagram. The angle will be,




Hence, the apparent frequency heard by the man from the train going away will be,






Hence, the apparent frequency heard by the man from the train coming towards will be,





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