Which of the following is not a type of lens?

A prism is not classified as a lens, which is why it is the correct answer to the question. Lenses are typically optical devices that help focus or disperse light through refraction. There are primarily three types of lenses: convex, concave, and meniscus.

Convex lenses are thicker in the center and thinner at the edges, converging light rays that pass through them. Concave lenses, on the other hand, are thinner in the center and thicker at the edges, diverging light rays. Meniscus lenses are curved and can be either convex or concave but are typically used to correct specific vision issues or in particular optical devices.

Prisms differ fundamentally in design and function. They do not focus or disperse light in the same way lenses do but instead refract light to bend it and separate it into different colors. This unique property of prisms allows them to create visual phenomena such as rainbows, but it is distinctly separate from the operating principles of lenses.