Investigating Waves with a Ripple Tank
- Ripple tanks are commonly used in experiments to demonstrate the following properties of water waves:
- Reflection at a plane surface
- Refraction due to a change in speed caused by a change in depth
- Diffraction due to a gap
- Diffraction due to an edge
Ripple Tank Apparatus
Reflection, refraction and diffraction can be demonstrated using a ripple tank
Investigating Reflection
- Reflection can be shown by the waves hitting a plane (straight) surface, such as a wall or mirror
Reflection in a Ripple Tank
Investigating Refraction
- Refraction can be shown by placing a glass block in the tank
- The glass block should sit below the surface of the water and cover only some of the tank floor
- The depth of water becomes shallower here the glass block is placed
- Since speed depends on depth, the ripples slow down when travelling over the block
- This is a good model of refraction showing how waves slow down when passing from deep water into shallow water
Refraction in a Ripple Tank
When water waves travel from deep areas to shallow areas they slow down
Investigating Diffraction
- Diffraction can be shown in a ripple tank by placing small barriers and obstacles in the tank
- As the water waves encounter two obstacles with a gap between them, the waves can be seen to spread out as follows:
Diffraction through a Gap in a Ripple Tank
Diffraction of water waves through a gap
- As the water waves encounter the edge of an obstacle, the waves can be seen to spread out as follows:
Diffraction round an Edge in a Ripple Tank
Diffraction of water waves after passing an edge
- The amount of diffraction depends on the size of the gap compared to the wavelength of the water wave
- The diagram below shows how the wavelengths differ with frequency in a ripple tank
- The higher the frequency of the motor, the shorter the wavelength
- The lower the frequency of the motor, the longer the wavelength
Generating Waves in a Ripple Tank
Ripple tank patterns for low and high frequency vibration
