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A plane progressive wave is given by y=2 cos 2π(330t-x) m. The frequency of the wave is

Asked in JEE Main 8th April 2nd Shift 2024 · Wave parameters from the equation

(1) 340 Hz
(2) 660 Hz
(3) 330 Hz
(4) 165 Hz

Answer: (3) 330 Hz

Step-by-step solution

Writing the argument as 2π(ft-x/λ), the coefficient of t inside the bracket is the frequency.

So f=330 Hz.

Why the other options are wrong

(1) Confuses the number with the speed of sound in air.
(2) Doubles the frequency, taking ω itself as 2π f twice over.
(4) Halves the frequency.

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