In a resonance column experiment, the first resonance is obtained when the level of the water in tube is 20…

In a resonance column experiment, the first resonance is obtained when the level of the water in tube is 20 cm from the open end. Resonance will also be obtained when the water level is at a distance of
  1. 40 cm from the open end
  2. 60 cm from the open end
  3. 80 cm from the open end
  4. 90 cm from the open end

Solution

Here, $\frac{\lambda}{4} = 20\text{ cm}$ (Diagram shows standing wave patterns in a tube open at one end with water column height corresponding to $\frac{\lambda}{4}$ and next resonance at $\frac{3\lambda}{4}$.) Next resonance will be obtained at $\frac{3\lambda}{4}$ or $60\text{ cm}$. So, resonance will be obtained when the water level is at a distance of $60\text{ cm}$ from the open end.

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