Which part of the eye is primarily responsible for detecting light and dark?

The rods are the part of the eye primarily responsible for detecting light and dark. They are photoreceptor cells located in the retina and are highly sensitive to light, allowing them to function well in low-light conditions. While rods do not detect color, they are crucial for viewing in dim lighting and for peripheral vision. Their ability to pick up on changes in light intensity makes them essential for night vision and for responding to varying levels of light throughout the day.

In contrast, cones are responsible for color vision and function best in brighter light conditions, while the lens is involved in focusing images onto the retina, and the cornea helps to refract light as it enters the eye. Therefore, the role of detecting light and dark falls squarely on the rods, highlighting their significance in our visual perception, particularly under low-light situations.