Final answer:
The reflection of light switches from diffuse to regular when water is spilled on ground glass because the water smooths out the glass surface, facilitating regular reflection.
Step-by-step explanation:
The reflection of light from a ground glass changes from diffuse to regular when you spill water on it due to the properties of the water and the glass involved. Light reflection occurs on the surfaces of materials. A ground glass has a rough surface, when light hits it, the light is scattered in many directions, this type of reflection is called diffuse reflection.
When water is spilled on the ground glass, it fills the tiny grooves and irregularities on the surface, making it smoother. This smooth surface allows the light to bounce off in the same direction or less scattered, which is known as regular reflection.
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