A car is moving along X-axis with a velocity `v=20m//s`. It sounds a whistle of frequency 660 Hz. If the speed of sound is `340m//s`. The apparent frequency heard by the observer `O` (shown in figure) is:

A car is travelling with a velocity of 40 m//s towards a source of sound of frequency 1000 Hz. If sound velocity is 330 m//s , then apparent frequency heard by the observer (in Hz) is

A train is moving with a uniform speed of 33 m//s and an observer is approaching the train with the same speed. If the train blows a whistle of frequency 1000 Hz and the velocity of sound is 333 m//s then the apparent frequency of the sound that the observer hears is

A train is moving with a uniform speed of 33 m/s and an observer is approaching the train with the same speed. If the train blows a whistle of frequency 1000 Hz and the velocity of sound is 333 m/s, then the apparent frequency of the sound that the observer hears is

An automobile moving at 30 m/s is approaching a factory whistle that has a frequency of 500 Hz. If the speed of the sound in air is 340 m/s, then the apparent frequency of the whistle as heard by the driver is

A source of sound is moving towards a high wall with a speed of 20 m/s. The frequency of the sound produced by the source is 400 Hz. If the speed of the sound is 340 m/s, then the beat frequency heard by a person standing near the wall will be