Answer: 80 dB.
- A 62 dB
- B 70 dB
- C 80 dB
- D 6000 dB
Correct answer: C. 80 dB
Explanation: Level in dB = 10 log(I/I<sub>0</sub>). Increasing I by 100 adds 10 log(100) = 20 dB, so the new level is 60 + 20 = 80 dB.
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.