Thanks! But I got a two more questions. If you are in for example a transparent aquarium filled with water, looking at some object through the aquarium wall, will the object be bigger or smaller? And the second question is that if you place an object right at the focus of a convex lens, where will the image appear. I think it will be either at the double focus length, between the lens and the object, or also at the focus, but on the other side of the lens?