A source of sound * and a detector D are placed at some distance from one another. A big cardboard is placed near the detector and perpendicular to the line SD as shown in figure. It is gradually moved away and it is shown that the intensity change from a maximum to a minimum as the board is moved through a distance of 20cm. What will be the frequency of the sound emitted. Velocity of sound in air is 336 ms-1.
(A) 420 Hz (B) 422 Hz (C) 450 Hz (D) 410 Hz
Correct option (A) 420 Hz
Explanation :
According to the given data V=336m/*,
λ / 4 =distance between maximum and minimum intensity
