Which statement about the Maddox rod's construction is true?

Which statement about the Maddox rod's construction is true?

• A. It uses cylindrical lenses to create a blue streak
• B. It is an array of prisms
• C. Composed of Plano convex lenses that causes a red streak in the opposite orientation as the ridges
• D. It neutralizes by prism over the fixating eye

Answer: (C)

The Maddox rod creates a line from a point light by using cylindrical lenses that bend light in only one meridian. This bank of cylindrical (essentially plano-convex in the cylindrical form) elements stretches the image into a streak, and the device is typically tinted so the streak appears red. The orientation of the streak is perpendicular to the axis of the cylinders, which is why the line runs opposite the ridges that indicate the cylinder axes. So, describing it as composed of plano-convex lenses that produce a red streak in the opposite orientation to the ridges fits how the Maddox rod works. It isn’t an array of prisms, and it doesn’t neutralize with a prism over the fixating eye, and the common observed streak color is red rather than blue.

The Maddox rod creates a line from a point light by using cylindrical lenses that bend light in only one meridian. This bank of cylindrical (essentially plano-convex in the cylindrical form) elements stretches the image into a streak, and the device is typically tinted so the streak appears red. The orientation of the streak is perpendicular to the axis of the cylinders, which is why the line runs opposite the ridges that indicate the cylinder axes. So, describing it as composed of plano-convex lenses that produce a red streak in the opposite orientation to the ridges fits how the Maddox rod works. It isn’t an array of prisms, and it doesn’t neutralize with a prism over the fixating eye, and the common observed streak color is red rather than blue.