Q.(a) Differentiate between rod and cone cells. OR

Rods handle dim-light, colourless vision and are spread across the retina, while cones handle bright-light, colour vision with high sharpness and are concentrated at the fovea.

Answering part (a): Differentiate between rod and cone cells.

Rod cells:

• Function in dim light (scotopic vision), being highly sensitive to even small amounts of light.
• Contain the visual pigment rhodopsin (visual purple), made of the protein opsin bound to retinal (derived from vitamin A).
• Provide only black-and-white (achromatic) vision — they cannot distinguish colours.
• Are far more numerous than cones (roughly 120 million in the human retina).
• Are distributed throughout the retina but are ABSENT from the fovea centralis (the retina's central point of sharpest vision).
• Give lower visual acuity (less sharp/detailed images) because many rods often converge onto a single bipolar/ganglion cell.

Cone cells:

• Function in bright light (photopic vision) and are less sensitive to dim light than rods.
• Contain the visual pigment iodopsin, of which there are three types (sensitive to red, green and blue wavelengths respectively), enabling colour vision.
• Provide sharp, high-resolution, colour vision. …