Question

The Swedish flag has a yellow cross on a blue back ground. How does it appear in red light? In blue light?

Red Light:
a) all black b) red cross on black background
c) magenta cross on green background

Blue Light:
a) all black b) magenta cross on a black background
c) black cross on a blue background

Answer 1

Yellow colour is made by red and green and it does not contain blue part.

so yellow colour will appear red in red light but black in blue light.

Blue colour contains only blue part in it.

So blue colour will appear blue in blue light but black in red light.

Now Part-1

Yellow cross on a blue background in red light will appear red cross on black background.

Answer is (B)

Now Part-2

Yellow cross on a blue background in blue light will appear black cross on blue background.

Answer is (C)