Answer 1

Given:
Speed of sound in air v = 340 m/s
Length of open organ pipe L = 20 cm = 20 × 10⁻² m
Fundamental frequency \[\left( f \right)\] of an open organ pipe :

\[f = \left( \frac{v}{2L} \right) = \frac{340}{2 \times 20 \times {10}^{- 2}}=850\text { Hz }\]

First overtone frequency \[\left( f_1 \right)\] : 

f₁ = \[2f\]

\[\Rightarrow  f_1  = \left( \frac{2V}{2I} \right) = 2 \times 850 = 1700 \text{ Hz }\]

Second overtone frequency \[\left( f_2 \right)\] : 

\[f_2  = 3f\]\[ \Rightarrow  f_2  = 3\left( \frac{V}{2L} \right) = 3 \times 850 = 2550  \text { Hz }\]