When prisms are placed in front of the eyes, which statement describes how light is bent and the retinal effect?

When prisms are placed in front of the eyes, which statement describes how light is bent and the retinal effect?

• A. The light passes straight through without deviation
• B. The light is reflected away from the base
• C. The light travels through the prism and is bent toward the apex
• D. The light travels through the prism and is bent toward the base

Answer: (D)

When light goes through a prism, it changes direction because it moves from one medium to another with a different refractive index. In ophthalmic prisms, the light is bent toward the base of the prism. This happens as the light enters the prism and again as it exits, but the overall effect is a deviation toward the base. On the retina, this means the image is shifted toward the base side, which is how the prism helps align the images seen by each eye. So, the correct statement is that light travels through the prism and is bent toward the base, producing a retinal shift toward that side. The other ideas—no deviation, light being reflected away from the base, or bending toward the apex—don’t match how refraction in a prism works or the typical retinal outcome.

When light goes through a prism, it changes direction because it moves from one medium to another with a different refractive index. In ophthalmic prisms, the light is bent toward the base of the prism. This happens as the light enters the prism and again as it exits, but the overall effect is a deviation toward the base. On the retina, this means the image is shifted toward the base side, which is how the prism helps align the images seen by each eye.

So, the correct statement is that light travels through the prism and is bent toward the base, producing a retinal shift toward that side. The other ideas—no deviation, light being reflected away from the base, or bending toward the apex—don’t match how refraction in a prism works or the typical retinal outcome.