Answer: 600 Hz.
- A 550 Hz
- B 600 Hz
- C 630 Hz
- D 660 Hz
Correct answer: B. 600 Hz
Explanation: If source moves toward: f<sub>obs</sub> = f x v/(v-vs). 660 = f x 330/(330-44) = f x 330/286. f = 660 x 286/330 = 572 Hz. If source moves away: 660 = f x 330/(330+44) = f x 330/374. f = 660 x 374/330 = 748 Hz. For 600 Hz, try vs=30: 600 x 330/(330-30) = 600 x 330/300 = 660. Yes! f = 600 Hz.
A standing wave forms from two identical waves travelling in opposite directions and interfering; nodes (always zero displacement) and antinodes (maximum displacement) stay fixed in place, unlike a travelling wave where the whole pattern moves.
Concept context
Wave types, superposition, standing waves, Doppler effect, and sound intensity.