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A string 2.0 m long and fixed at its ends is driven by a 240 Hz vibrator. The string vibrates in its third harmonic mode. The speed of the wave and its fundamental frequency is :

1. 320 m/s, 80 Hz
2. 180 m/s, 120 Hz
3. 320 m/s, 120 Hz
4. 180 m/s, 80 Hz

Correct answer: 320 m/s, 80 Hz

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