Snell's Law Predicts Linear Graph Steps:

• Recall Snell's law: sin i / sin r = n (refractive index of glass, constant).
• Rearrange to sin i = n sin r, a linear equation y = mx where m = n.
• Plot sin i (y-axis) vs. sin r (x-axis): straight line through origin with slope n.
• Experimental data should approximate this line, confirming the graph.

Why A is correct:

• A shows a straight line through origin, matching sin i = n sin r from Snell's law.

Why the others are wrong:

• B: Curved line violates constant n in Snell's law.
• C: Horizontal line implies sin i constant, ignoring varying r.
• D: Line not through origin suggests incorrect zero-angle refraction.

Final answer: A