Which of the following best describes the relationship between specific gravity and refractive index for a series of liquids?

• A. A parabolic curve where refractive index increases rapidly at low specific gravity and then levels off.
• B. A horizontal line indicating no relationship between specific gravity and refractive index.
• C. A linear graph where both specific gravity and refractive index increase proportionally.
• D. A graph with a negative slope, showing that as specific gravity increases, refractive index decreases.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the properties involved. Specific gravity is a measure of the density of a liquid relative to water, while refractive index measures how much light bends when passing through the liquid.
2. Step 2: Consider the physical basis of the relationship. Both specific gravity and refractive index depend on the molecular composition and structure of the liquid, which often change together in a predictable way.
3. Step 3: Analyze the options given. A linear relationship suggests that as the density (specific gravity) increases, the refractive index also increases proportionally, which is common for many liquids with similar molecular types.
4. Step 4: Evaluate why other options are less likely. A parabolic curve or a negative slope would imply non-intuitive or inverse relationships that are not typically observed for a series of similar liquids.
5. Step 5: Conclude that the best description is a linear graph where both specific gravity and refractive index increase proportionally, reflecting their correlated dependence on molecular properties.