Answer 1

Given:
Separation between the node and anti-node = 25 cm
Speed of sound in air v = 340 ms⁻¹
Frequency of vibration of the air column f = ?
The distance between two nodes or anti-nodes is λ.
We have : 

\[\frac{\lambda}{4} = 25  \text { cm }\] 

\[ \Rightarrow   \lambda = 100  \text { cm } = 1  \text { m }\]

Also ,

\[v = f\lambda\]

\[\Rightarrow   f = \frac{v}{\lambda} = \frac{340}{1} = 340  \text { Hz }\]

Hence, the frequency of vibration of the air column is 340 Hz.