A small source of sound vibrating at frequency $$ 500\,Hz $$ is rotated in a circle of radius $$ 100/ \pi \, cm $$ at a constant angular speed of $$ 5.0 $$ revolutions per second. The speed of sound in air is $$ 330\, m/s $$.
For an observer situated at a great distance on a straight line perpendicular to the plane of the circle , through its centre , the apparent frequency of the source will be
greater for half the circle and smaller during the other half
The correct option is C always remain $$ 500\,Hz $$
Since the source is moving on a small circle in a plane perpendicular to the direction of the wave the observer located on the axis of the circle , there would be no change in the observed frequency which will be the same as the real frequency , i.e., $$ 500 \,Hz $$