Wave diffraction experiment. Waves in a ripple tank passing through an aperture, demonstrating the principle of diffraction. Plane waves are generated on the surface of the water at bottom. When these waves pass through a large aperture (lower centre), they change shape and form flattened concentric waves (upper frame) centred on the aperture. The amount by which the waves change shape depends on the size of the aperture. Diffraction is greatest when the aperture size is similar to the wavelength. This is seen in A180/225, where waves of the same wavelength as seen here are passing through a smaller aperture. Applications of diffraction include gaps used to focus and spread sound and radio waves.