Why does a green apple appear black under a red light?

When a green Apple appears black under a red light, it is because the red light does not contain wavelengths that correspond to the green color of the Apple. The red light is absorbed by the Apple, causing it to appear black as there is no green light being reflected off the surface to be perceived by our eyes. Each color of light corresponds to a specific wavelength, and when the light's wavelength does not match the object's color, the object will appear different.