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

• A

  40 cm from the open end
• Correct answer
  B

  60 cm from the open end
• C

  80 cm from the open end
• D

  90 cm from the open end

Solution

Given, $\frac{\lambda}{4}=20 \mathrm{~cm}$

Next resonance will be obtained at $\frac{3 \lambda}{4}=60 \mathrm{~cm}$

Hence, the correct answer is option: 'B'.