Light travels from water, with index 1.333, into an unknown substance. The incident angle is 45.00 degrees and the measured angle of refraction is 40.30 degrees. Using n1 sin(theta1) equals n2 sin(theta2), what is the unknown substance's index, and what does the table suggest it is?

1. Snell's law rearranges to n2 = n1 sin(theta1) / sin(theta2). 2. Substituting values: n2 = (1.333)(sin 45.00°) / (sin 40.30°) = (1.333)(0.7071) / (0.6468). 3. Carrying out the arithmetic gives n2 = 1.457. 4. The table of indices lists fused quartz at n = 1.458, the closest match to this computed value. 5. The smaller theta2 compared with theta1 shows the ray bent toward the normal, which fits a substance with a higher index than water, ruling out n2 = 1.333. 6. n2 = 1.921 and n2 = 1.000 are far from the computed value and do not follow from the given angles. _Source: OpenStax Physics (CC BY 4.0), Ch 16 "Mirrors and Lenses", section 16.2 Refraction_