JAMB - Physics (1989 - No. 20)
When a yellow card is observed through a blue glass, the card would appear.
black
green
red
white
Vysvetlenie
Yellow light is a mixture of red and green light, hence, yellow will reflect red and green light. This means that a yellow object will appear red under red light, and green under green light. Yellow does not contain blue, so it will appear black under blue light.