If the retinal image remains constant, the distance to the object is:

• A. Moving closer
• B. At a fixed distance
• C. Moving away
• D. The size is increasing

Answer: (B)

The key idea is how the size of what you see on the retina relates to distance. The image on the retina (the angular size) stays the same only if the eye-object distance doesn’t change, assuming the object’s actual size stays the same. Since angular size is roughly proportional to object size divided by distance, a constant retinal image means distance is fixed. If you moved closer, the retinal image would get larger; if you moved away, it would get smaller; and changing the object’s size would change the retinal image too. So the distance to the object remains constant.