A whistle (supplied by a stream of air) emitting sound at 3.00 kHz is fixed to a rotating blade 1.60 m from the axis of rotation. The blade spins in a horizontal circle at 360 rpm. If the sound undergoes the Doppler effect, work out the greatest and least frequencies detected by an observer.

• A. f₊ = 3640 Hzf_- = 2550 Hz
• B. f₊ = 3640 Hzf_- = 3530 Hz
• C. f₊ = 3530Hzf_- = 2470 Hz
• D. f₊ = 3530 Hzf_- = 2550 Hz

Answer: (A)