I observed following phenomena today: in my room with some lightings, there is a stuff toy placed in front of a wall. The ambient lighting doesn't cause any shadow on the wall currently. Now, I switched ON a torch and pointed it to a stuff toy which was kept in front of a wall and a shadow appears on the wall. Later, I increased the light intensity of the torch falling on the toy and observed that the shadow on the wall has become darker. However, I didn't observe this phenomena when I switched of all the lights of my room and repeated the experiment. As far as I have understood, the directed light from torch tries to cut-off the ambient light on the wall. The more the intensity of torch light is, the more ambient light gets cut-off. I will be really grateful if somebody can formally explain this phenomena to me with all the physics laws involved, preferably with some links or illustrations on the topic.