American Buddhismâs numbers are booming. Published just over three years ago, an American Religious Identification Survey survey showed that from the years 1990 to 2000, Buddhism grew 170 percent in North America.
However, for a lens, a positive image distance implies that the image is located on the opposite side as the object. Virtual images are formed by concave lenses or by placing an object inside the focal length of a convex lens. The ray-tracing exercise is repeated for the case of a virtual image. In this case the virtual image is upright and shrunken. The same formula for the image and object distances used above applies again here.
As soon as any of the angles becomes less than 180 then you are dealing with a concave shape. This is a good mathematical test that is easy to code against. Convex and Concave in 3D. Hopefully, by this point, you are starting to get a decent idea of what makes a 2D shape concave vs convex.