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