Question

Explain why objects are seen more dearly at night by not looking directly at them?

Answer 1

The rods, responsible for vision in the dark, are mostly present in the periphery of the retina which is responsible for peripheral vision. Hence, less focus on objects in the dark provides a clearer vision as the light is projected on the rods.

Complete answer:
Retina contains the photoreceptor cells which convert light energy to electrical impulses by activating a series of light sensitive cells called rods and cones. The macula comprises the central part of the eye which primarily consist of cone cells. They produce sharp images of the object which are aimed directly towards the eye, especially in bright lights. The rest of the retina is responsible for peripheral vision which allows the eye to see objects off to the sides from the point of focus.

The periphery of the retina mostly comprises rod cells. These cells are much more sensitive in the dark than cones and mostly responsible for vision in the dark. Since these cells are mostly found in the region of peripheral vision of the cell, faint objects can often be seen more clearly in the dark if the eyes are not aimed directly at them. For example, watching the sides of a dim star makes its image fall on the peripheral region of the retina that has mostly rods and provides the best vision of the star in the dim lights.

Additional information:
The eye allows us to see and interpret the shapes, colours and dimensions of objects by processing the light they reflect. The eye changes light rays to electrical impulses which are carried to the brain for interpretation through the optic nerve. The brain then interprets these electric impulses to visual images. Six muscles are responsible for the movement of the eye. The most important parts of an eye include the cornea, iris, lens, conjunctiva, retina, macula and the optic nerve.

Note: Cone cells are responsible for colour information and sharpness of the image while rod cells highly sensitive detectors of white light help in night vision. The number of rod cells present in the retina is much higher than that of cone cells.