The graph between angle of deviation (δ) and angle of incidence (i) for a prism is a curve, not a straight line. As i increases from a small value, δ first decreases, reaches a minimum value, and then increases again. This minimum deviation occurs when the light ray passes symmetrically through the prism. The graph is a smooth, U-shaped (or V-shaped) curve with a single minimum point. The correct option is the one that depicts this non-linear curve with a clear minimum.

Final Answer: The second graph (U-shaped curve with a minimum)