JEE Main 2019 Physics question
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:
Answer: (A)
Solution
λ = 2L/3 = 4/3 m, v = 240 × 4/3 = 320 m/s; = 240/3 = 80 Hz.