# To measure the speed of waves on the water surface

If you make a disturbance in the otherwise calm surface of a liquid, the disturbance travels on the surface at certain speed. The speed depends on surface tension, the height of the liquid from the bottom (assumed to be fixed), density, bulk modulus etc. This experiment is to get the wave speed on water kept in a container.

The objective of this experiment is to measure the speed of waves on the water surface. You need a water bottle with glucose drip connected, a container (thali), a stop watch or mobile watch.

## Procedure

1. Look at the arrangement given. A glucose drip needle is inserted in the water bottle given. A regulator is given to control the rate at which water drops come out of the open end of the tube.
2. Put water in the given thali to have 1.0 cm thick water mass. Place the container with its center just below the open end of the tube. This is to ensure that the drops fall at the center of the Thali.
3. Open the regulator slightly so that drops fall on the water in the Thali. You will see circular waves spreading from the center, moving towards the periphery of the container and reflecting from there. The reflected wave will converge at the center and again spread with a smaller amplitude.
4. Adjust the regulator so that a drop falls exactly at the same time when the wave from the previous drop converges to the center after reflection. In this case, the time interval between successive drops is the same as the time taken by the wave to go from the center to the periphery and back.
5. Find the time interval between successive drops.
6. Measuring the diameter of the container, calculate the speed of waves on the surface of the water.

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