Describe the concepts of reflection, refraction, diffraction and superposition.

Describe the process of diffraction in water waves.

A student observes water waves in a ripple tank passing through a narrow gap in a barrier. After passing through the gap, the waves spread into the region beyond the barrier rather than continuing in straight lines. Describe the wave phenomenon observed and explain how the width of the gap affects the degree to which this phenomenon occurs.

A plane wavefront travelling through air strikes a flat glass surface at an angle of incidence of \(30^\circ\). The refractive index of the glass is \(1.5\). Which diagram correctly describes the change in wavefront direction and spacing as the wave enters the glass?

A student investigates wave behaviour using a ripple tank. In the first trial, plane waves travel from deep water into shallow water at an oblique angle and change direction. In the second trial, plane waves encounter a barrier with a narrow gap and spread into the shadow region beyond the gap. In the third trial, two identical waves travel through the same region simultaneously. Compare the wave phenomena observed in the three trials, identifying which concept is demonstrated in each case.