Answer: f obs = f(v+v o )/v.
- A f<sub>obs</sub> = f(v-v<sub>o</sub>)/v
- B f<sub>obs</sub> = f(v+v<sub>o</sub>)/v
- C f<sub>obs</sub> = fv/(v+v<sub>o</sub>)
- D f<sub>obs</sub> = f x v<sub>o</sub>/v
Correct answer: B. f<sub>obs</sub> = f(v+v<sub>o</sub>)/v
Explanation: Observer moves toward source: effective speed of sound increases. f<sub>obs</sub> = f(v + v<sub>o</sub>)/v.
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.