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.
estigués de fet a l'ombra, i reflectint la mateixa quantitat de llum als vostres ulls com la que està fora de l'ombra, hauria de ser més reflectant – simples lleis de la física.