Two identical piano wires, when tuned to a fundamental frequency of 400 Hz, produce no beats. One wire is then slightly tightened, and the beat frequency heard is 2 Hz. What is the new fundamental frequency of the tightened wire?
Step 1: Concept The frequency of a stretched string $n$ is directly proportional to the square root of its tension ($n \propto \sqrt{T}$).
Step 2: Meaning Tightening a wire increases its tension, which necessarily increases its frequency.
Step 3: Analysis Beat frequency is the difference between two frequencies ($|n_1 - n_2| = 2$ Hz). Since the wire was tightened, the new frequency must be $400 + 2 = 402$ Hz.
Step 4: Conclusion The new fundamental frequency is 402 Hz.
Final Answer: (B)