Two loudspeaker `M` and `N` are located `20m` apart and emit sound at frequencies
Channel: Doubtnut
Date: 05/07/2020

Two loudspeaker `M` and `N` are located `20m` apart and emit sound at frequencies `118Hz` and `121Hz`, respectively. A car is intially at a point `P`, `1800m` away from the midpoint `Q` of the line MN` and moves towards `Q` constantly at `60 km//hr` along the perpedicular bisector of `MN`. it crosses `Q` and eventually reaches a point `R`, `1800m` away from `Q`. let `v(t)` represent the beat frequency measured by a person sitting in the car at time `t`. let `v_(P)`, `v_(Q) and v_(R)` be the beat frequencies measured at locations `P`,`Q` and R`, respectively. the speed of sound in air is `330ms^(-1)`. which of the following statement (s) is (are) true regarding the sound heard by the person?