Final answer:
A red apple will appear black when illuminated by blue light, as it absorbs all the blue and does not reflect any light back to the viewer.
Step-by-step explanation:
The question asks which color light will make a red apple appear black. When a red object is illuminated by blue light, it appears black because red objects absorb blue light. Blue light has a short wavelength and when it shines on a red object, which can only reflect red light, all of the blue light is absorbed and none is reflected be seen. Hence, under blue light, a red apple would not reflect any light and would appear black to our eyes.
Answer Choices:
A. Red light - The apple will appear red because red light would be reflected.
B. Blue light - The apple will appear black because all of the blue light would be absorbed.
C. Green light - The apple will appear darker as it absorbs most of the green light but may not be entirely black.
D. None of the above - Incorrect because blue light will make the apple appear black.
In summary, a red apple will appear black under option B. Blue light because it absorbs the blue light and reflects no light back to the viewer's eyes.