What happens to a light ray's direction when it changes speed while crossing a boundary between two media?
AIts direction only changes if the two media are both solid
BIts direction stays exactly the same regardless of the speed change
CIts direction also changes, and the effect is called refraction
DIts direction reverses completely, sending it back the way it came
Answer & Solution
Correct answer: C. Its direction also changes, and the effect is called refraction
1. When light changes speed while crossing a boundary between media, it also changes direction.
2. The greater the difference in speeds, the more the path of light bends.
3. This bending is introduced here as refraction and is examined in more detail in a later chapter.
4. The direction does not stay fixed and does not reverse outright, so those options are wrong.
_Source: OpenStax Physics (CC BY 4.0), Ch 15 "Light", section 15.2 The Behavior of Electromagnetic Radiation_
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