why the answer is false? F.3 Physics (optics)

A yellow object only reflects yellow light that reaches your eyes to be perceived as yellow color. All other colors of light are absorbed by the object.

"A yellow object can only reflect red and green lights"
"why it's wrong?"
The statement is wrong simply because a yellow object can not reflect red and green lights.

but "red+green= yellow"
This is another story. If red and green are mixed before reaching the surface of the yellow object, the mixed light will become yellow ahead of the contact. It will be a yellow light shedding on the yellow object then, not red and green anymore. So the yellow light reflects.
Any red or green light reaching the surface of the yellow object will be absorbed. There is no way they can be reflected at all.

* why it's wrong? red+green= yellow

nothing wrong
because the colour of light is different
光既混合同你用既顏料既混合係唔同的

2008-10-28 21:41:33 補充：
所以 紅光+綠光=黃光
係正確無誤的

A yellow object can only reflect yellow light
除左yellow,其他色係會absorb左

黃色係冇得溝出泥的

2008-10-28 21:33:52 補充：
可見光有紅,橙,黃,綠,藍,靛,紫

BLUE+GREEN=YELLOW YOU IDIOT