After the 1600s, observations of light being refracted caused scientists to begin believing that light acted as:

• A. They began to believe that light acted as waves.
• B. They no longer believed that light acted as waves.
• C. They began to believe that light acted as particles.
• D. They no longer believed that light acted as particles.

Answer: (A)

Observations of light bending at boundaries point to light behaving as waves. When light moves from one medium to another, its speed changes, and in a wave picture that change causes the wavefronts to tilt, making the light ray bend toward or away from the normal depending on the media. This is encapsulated in Snell's law, which ties the angles to the speeds of light in the two media and explains why refraction occurs so naturally for different colors as well. The wave view also accounts for dispersion—different wavelengths slowing by different amounts—something that aligns with experimental results after the 1600s. While a particle view can be made to fit some aspects, the wave explanation provides the clean, consistent account of refraction that scientists found compelling at the time.