When a lighted matchstick is shown before another light source, the shadow of the matchstick is formed on a screen but not the shadow of the flame. Why is it so?

A shadow is a lightless (dark) region formed beyond an opaque object in the direction opposite to the source of light. An opaque object that comes in the way of light prevents the light that is due to fall beyond it resulting in the formation of shadow.

When a lighted matchstick is shown before a source of light, the matchstick, being opaque obstructs the light from the source and acts a shadow of it on a screen. The flame of the matchstick itself is a source of light. The flame throws its own light to fall on the region beyond it and cannot prevent the light from the other source too. Hence the shadow of the flame is not formed. Courtesy : The Hindu