Now the shadow level is set to 50. This lets half the light travel through an object (that's what a lower shadow intensity means - it's an unrealistic render trick).

Now the ground behind the block is partially lit. And so is the ball. There'd be no reason you should be able to see these in a real world equivalent to this setup (you can try it at home ;-)).

Note how the unlit portions of the block (the sides and top) are so much darker than the ground immediately behind. This is unrealistic.