Answer:
The length of the tube is 85 cm
Explanation:
Given;
speed of sound, v = 340 m/s
first harmonic of open-closed tube is given by;
N----->A , L= λ/₄
λ₁ = 4L
v = Fλ
F = v / λ
F₁ = v/4L
Second harmonic of open-closed tube is given by;
L = N-----N + N-----A, L = (³/₄)λ

Third harmonic of open-closed tube is given by;
L = N------N + N-----N + N-----A, L = (⁵/₄)λ

The difference between second harmonic and first harmonic;

The difference between third harmonic and second harmonic;

Thus, the difference between successive harmonic of open-closed tube is
v / 2L.

Therefore, the length of the tube is 85 cm