Why does a stationary wave form at a free end of a water tank?

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A stationary wave forms at the free end of a water tank due to the superposition of incoming and reflected waves. When the wave reaches the tank's right side, it creates an antinode because the water surface is free to move vertically. This contrasts with a closed pipe, where a node forms at the closed end due to the air being constrained. The distinction lies in the nature of the waves; water waves are transverse, allowing vertical movement, while sound waves are longitudinal, restricting movement at closed ends. Understanding this difference clarifies why an antinode occurs at the tank's edge.
songoku
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This is the set up to produce stationary wave. The oscillator on the left will produce wave on water surface then this wave will travel to right, reflected at the tank and the incoming and reflected wave will superpose to form stationary wave.

My teacher said when the water wave hits the tank at the right side, antinode of stationary wave will be formed because it is a free end. I don't understand why it is a free end, I thought it as a fixed end since the tank is a rigid container. My analogy is at the closed end of a closed pipe, node is always formed, not antinode so why at the tank an antinode is formed?

Thanks
 
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songoku said:
My analogy is at the closed end of a closed pipe, node is always formed, not antinode so why at the tank an antinode is formed?
This is the difference between a transverse wave and longitudinal one.

Water waves are transverse; the water level moves up and down while the wave propagates sideways and at the edge of the tank the water is free to move up and down.

Sound waves are longitudinal; the air moves back and forth and at the end of the closed pipe is constrained not to be able to move.
 
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Thank you very much Nugatory
 

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