IOR stands for the ratio of speed of light in a vacuum to the speed of light in what material?

IOR stands for the ratio of speed of light in a vacuum to the speed of light in what material?

• A. Air
• B. Water
• C. Glass
• D. Plastic

Answer: (C)

Index of refraction is defined as the speed of light in vacuum divided by the speed of light in the material. Since light slows more in denser materials, the ratio c/v gets larger with higher n. For air, that ratio is almost 1 because light barely slows; for water it’s about 1.33; for glass it’s about 1.5; and for many plastics it ranges around 1.5 to 1.6. Among the given options, glass has a typical index near 1.5, so the ratio c/v in glass matches the common IOR value. That’s why glass is the best match.

Index of refraction is defined as the speed of light in vacuum divided by the speed of light in the material. Since light slows more in denser materials, the ratio c/v gets larger with higher n. For air, that ratio is almost 1 because light barely slows; for water it’s about 1.33; for glass it’s about 1.5; and for many plastics it ranges around 1.5 to 1.6. Among the given options, glass has a typical index near 1.5, so the ratio c/v in glass matches the common IOR value. That’s why glass is the best match.