Differentiate between the following on the basis of what is given in brackets.
Rod cells and Cone cells (pigment)

Hint: Hearing, sight, smell, taste, and touch are the five traditional human senses classified and universally by Aristotle and Gautama Buddha. One of the functions of the nervous system is processing sensory information. The sensory nervous system contains neural pathways, sensory neurons, and portions of the brain concerned with sensory perception.

Complete answer:
Human eye considered to be the primary part of the sensory nervous system. The human eye reacts to light and visualizes objects in front of them. The rods and cons cells present in the retina allow light perception, vision, and colour differentiation. The human eye consists of the cornea, pupil, lens, retina, ciliary muscles, and optic nerve. Photons of light energy enter into the eye through the cornea, pupil, and then the lens before they fall on the photoreceptors (cones and rods) present in the retina of the eye. These photoreceptors absorb and convert light energy to electrical signals which are transferred by the optic nerve to the brain for interpretation.

RODS: These are rod-like photoreceptors that provide twilight vision, i.e. their main function is to provide vision during dim light or night which is also known as scotopic vision. They are located at the boundary of the retina. Rod cells do not provide colour vision. Rods have an outer cylindrical segment which comprises the pigment called rhodopsin. Rhodopsin is made up of vitamin A and lack of this pigment could result in night blindness.
CONES: These are cone-shaped photoreceptors present in the center of the retina and are cone-shaped. They provide a photopic vision, i.e. they allow vision in daylight or in bright light. Cones function other than photopic vision is to provide a colour vision of three types that is green, blue, and red. Cones have an outer conical segment which consists of the colored pigment called Iodopsin. Lack of this pigment could result in colour blindness.
Therefore, the main difference between rods and cones on the basis of pigments is that Rods contain rhodopsin and cones contain iodopsin.

Note: There are about 125 million photoreceptors present in the human eye retina. Out of these 120 million are rods and about 5 million are cones. They absorb light energy and convert it into electrical signals. The human eye has the ability to differentiate between 10 million colours.