What are the circular spots of light on the ground beneath a tree on a sunny day?

The circular spots of light on the ground beneath a tree on a sunny day are indeed pinhole images of the Sun. This phenomenon occurs because sunlight filters through the gaps between the leaves. When the sunlight passes through these small openings, it creates a series of circular spots or images on the ground that resemble the shape of the sun itself. Each gap acts as a tiny pinhole, allowing light to project through and form these images.

In this context, the pinhole effect is similar to how a pinhole camera works, where light from a bright source (the Sun) travels in straight lines through small openings, casting a focused image on a surface. As the sun moves across the sky, these spots can shift and change in size and shape, but they retain their circular nature as long as the gaps in the leaves remain consistent.

The other choices involve concepts that do not fit this specific situation. Reflections of the Moon, for instance, would not create circular spots on the ground during the day when the Sun is shining bright. Shadows from tree leaves typically create more solid shapes rather than light spots. Cloud reflections would also not be localized in this manner beneath a tree, as they would not result in distinct pinhole images of sunlight.