Look at the spherical mirrors from various angles. Notice that the image in each mirror is a little different from the image in the neighboring mirrors. Notice that if you point your finger at one sphere, the image of your finger in all the other mirrors will point at the chosen mirror. Also notice that your image is very small in the mirrors, and that it appears quite far away. Each Christmas tree ball is a convex mirror - a mirror that curves out toward the source of light.
Convex mirrors reflect images that are smaller than life-sized.
In the ray diagram above, notice the reflection of two rays of light from a particular point at the tip of the pencil. Your eye and brain follow these reflected rays backward along a straight line to their apparent intersection behind the mirror. All other reflected rays from the point also seem to originate at this intersection. The reflected rays from all other points on the pencil also appear to intersect at specific points behind the mirror. All these intersection points put together create what's called a virtual image.