A source of sound S emitting waves of frequency 100 Hz and an observer O are located at some distance from each other. The source is moving with a speed of 19.4 m s^$$-$$1 at an angle of 60^o with the source observer line as shown in the figure. The observer is at rest. The apparent frequency observed by the observer (velocity of sound in air 330 m s^$$-$$1), is

The fundamental frequency of a closed organ pipe of length 20 cm is equal to the second overtone of an organ pipe open at both the ends. The length of organ pipe open at both the ends is

If n₁, n₂ and n₃ are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency n of the string is given by

A speeding motorcyclist sees traffic jam ahead him. He slows down to 36 km hour^$$-$$1. He finds that traffic has eased and a car moving ahead of him at 18 km hour^$$-$$1 is honking at a frequency of 1392 Hz. If the speed of sound is 343 m s^$$-$$1, the frequency of the honk as heard by him will be