Which tool consists of a transparent solid with two nonparallel plane faces and is used to change light's direction?

A prism is a transparent optical element that has two nonparallel plane faces. Its primary function is to refract or bend light, altering its direction. When light passes through a prism, the change in its speed as it moves from one medium to another—air to glass, for example—causes it to bend according to the principles of refraction. The specific angle and orientation of the prism determine how much the light will change direction.

This property of the prism is utilized in various optical applications, such as in glasses for correcting vision, in optical instruments, and even in creating visual effects in photography. The design allows it to disperse light into its constituent colors—creating a spectrum—which is an important aspect in both scientific applications and artistic endeavors.

Other options, while related to optics, serve different purposes: ptosis refers to the drooping of the upper eyelid and is not an optical tool; convex and concave refer to the shapes of lenses or mirrors but do not specifically entail changing light direction in the same manner as a prism. A convex lens, for instance, converges light rays to a point, while a concave lens diverges them, but neither has the unique nonparallel faces that define a prism's action of ref