Answer: 11.5 Hz, 29.83 m
Explanation:
Given
Linear density of the cable, μ = 0.2 kg/m
Tensión in the cables, T = 500 N
Wavelength of the wave, = 4.5 Waves
Distance between the poles, L = 20 m
Temperature of, t = 20° C
Speed of sound, v = 343 m/s
λ = length / number of waves =
λ = 20 / 4.5
λ = 4.44 m
Frequency of a standing wave is the same as frequency of a hum. Calculated using the formula
F = n/2L * √(T/μ)
F = 1/λ * √(T/μ)
F = 1/4.44 * √(500/0.2)
F = 0.23 * √2500
F = 0.23 * 50
F = 11.5 Hz
Wavelength of the hum,
λ = v/f
λ = 343 / 11.5
λ = 29.83 m