Concept:A ripple tank is used to show how waves behave when they meet barriers, change depth, or pass through openings.
Explanation:A ripple tank uses water waves with a strobe light so wave patterns are clearly visible on a screen below the tank.
Reflection (I) can be demonstrated by placing a straight barrier in the tank and observing the waves rebound from it at the same angle.
Refraction (II) can be demonstrated by placing a flat glass plate under the water to make the depth shallower in one region, causing the waves to slow down and bend as they cross the boundary.
Diffraction (III) can be demonstrated by placing two obstacles to make a narrow gap and watching the waves spread out after passing through the gap.
Since I, II, and III are all observable with a ripple tank, the correct option is A.
Answer:A. I, II and III