Drag the point f (light blue) to change the focal length of the lens. Drag it to the opposite side of the lens to change the lens type.[br]Drag the point E (light blue) to change the location (horizontal drag) and height (vertical drag) of the object.[br][br]The thickness of the lens does NOT correspond to the focal length.

What phenomenon does the failure of all 3 lines to cross neatly at a single point demonstrate?[br]When is the image right side up?[br]When is the image real?[br]When is the image larger than the object?[br]What happens when you drag f through the lens to the other side? How is that related to the sign conventions for lenses?