If you can't see an object it hasn't reflected light into your eye.

your eyes have light senseitive sells which senses the light, they send a message to the brain to creat a picture(which is upside-down and the brain turnes it around).

light reflects back off an opaque object

(which is an objectthat is coloured all the

way through) and then it makes a shadow

because no light can reach there.The eye's Iris contracts to let less light through and expands to let more light through your eye.