Which term is a measure of the change in the speed and angle of light as it passes from one material to another?

Which term is a measure of the change in the speed and angle of light as it passes from one material to another?

• A. Proportions
• B. Recovery
• C. Refractive index (RI)
• D. Relief

Answer: (C)

Light slows down and bends when it crosses from one material to another, and the term that captures both of these effects is the refractive index. It’s a dimensionless quantity that compares how fast light travels in vacuum to how fast it travels in the material. This speed difference directly relates to the bending of the light, described by Snell’s law: the product of the incident angle and the refractive index of the first medium equals the product of the refracted angle and the refractive index of the second medium (n1 sin θ1 = n2 sin θ2). So higher refractive index means light slows more and bends more toward the normal when entering, while entering a lower-index material makes it speed up and bend away from the normal. For example, air is about 1.0003, water about 1.333, and glass around 1.5, illustrating how the index quantifies both the speed change and the directional change. Other terms like proportions, recovery, or relief don’t describe this relationship between speed, direction, and boundary crossing.

Light slows down and bends when it crosses from one material to another, and the term that captures both of these effects is the refractive index. It’s a dimensionless quantity that compares how fast light travels in vacuum to how fast it travels in the material. This speed difference directly relates to the bending of the light, described by Snell’s law: the product of the incident angle and the refractive index of the first medium equals the product of the refracted angle and the refractive index of the second medium (n1 sin θ1 = n2 sin θ2). So higher refractive index means light slows more and bends more toward the normal when entering, while entering a lower-index material makes it speed up and bend away from the normal. For example, air is about 1.0003, water about 1.333, and glass around 1.5, illustrating how the index quantifies both the speed change and the directional change. Other terms like proportions, recovery, or relief don’t describe this relationship between speed, direction, and boundary crossing.