Because if the tile in that shadow were in fact in shadow, and reflecting the same amount of light to your eye as the one outside the shadow, it would have to be more reflective -- just the laws of physics.
benar-benar dalam bayangan dan memantulkan jumlah cahaya yang sama ke mata Anda seperti ubin di luar bayangan itu, ubin akan memantulkan cahaya lebih -- fisika dasar.