Which statement best describes Cleo's mistake about light entering water from air?

Which statement best describes Cleo's mistake about light entering water from air?

• A. Light travels through air and water in angled, scattered paths.
• B. Light does not change direction when moving from air into water.
• C. Light slows down when it moves from air into water.
• D. Light bends toward the normal when it moves from air into water.

Answer: (C)

Light changes speed when it crosses from one medium to another. Entering water from air, light slows down because water has a higher optical density (refractive index) than air. That change in speed is what causes refraction, so the ray bends toward the normal if it hits at an angle. Cleo’s mistake is missing this speed change; recognizing that light slows down in water is the accurate description of what happens and explains why the ray changes direction. The idea that light wouldn’t slow down (or would speed up) would lead to a misunderstanding of why refraction occurs.

Light changes speed when it crosses from one medium to another. Entering water from air, light slows down because water has a higher optical density (refractive index) than air. That change in speed is what causes refraction, so the ray bends toward the normal if it hits at an angle. Cleo’s mistake is missing this speed change; recognizing that light slows down in water is the accurate description of what happens and explains why the ray changes direction. The idea that light wouldn’t slow down (or would speed up) would lead to a misunderstanding of why refraction occurs.