A group of 8 suspects; 3 wearing red shirts, 2 wearing green shirts and 3 wearing blue shirts. Eye-witness claims to have seen 3 people in the scene, the shirt of one of them appeared red, while the rest appeared black. The lighting at the scene was by a monochromatic red light source.
Now, the crazy executioner decides he's going to pick one of those suspects at random for early judgement. Based on the witness's testimony, can you give the executioner any advice which will increase his odds of picking a culprit?
Monochromatic light is light which is of only 1 uniform frequency or wavelength; so it can't be split any further. For example, sodium street lamps emit monochromatic yellow-ish light, and so it only reflects off yellow or partially yellow objects, making them the only things to be seen colored.