Final answer:
When illuminated with blue light, a sheet of red paper will look black because the red paper absorbs all the blue light and reflects only the red and green components of the light.
Step-by-step explanation:
A sheet of red paper will look black when illuminated with blue light. This is because when illuminated with blue light, the red paper will absorb all the blue light and reflects only the red and green components of the light. Since red paper absorbs all the blue light, it appears black to our eyes.