Destructive Interference Conditions

Steps:

• No sound at a point indicates destructive interference between waves from the two speakers.
• Destructive interference requires waves to arrive out of phase by an odd multiple of π radians.
• Path length difference can provide phase shift, so emission phase isn't fixed.
• Same frequency and amplitude ensure stable interference and complete cancellation.

Why A is correct:

• Waves emitted out of phase can still destructively interfere at points where path difference compensates for the initial phase offset.

Why the others are wrong:

• B: Similar amplitude is needed for complete cancellation to produce zero sound intensity.
• C: Same frequency is required for waves to maintain a consistent phase relationship and form an interference pattern.
• D: Same wavelength (tied to frequency in air) is essential for predictable path difference effects in interference.

Final answer: A