A: Nocturnal animals equivalent to cats are tailored to dim mild. Their retina has extra rod cells, which assist scotopic imaginative and prescient or imaginative and prescient below darkish circumstances, than cone cells, which assist photopic imaginative and prescient or imaginative and prescient below vibrant mild.
Behind their retina is a layer known as the choroid coat, which has a reflective floor known as the tapetum lucidum (Latin for ‘shiny carpet’). The cells of the tapetum lucidum are fabricated from reflective supplies equivalent to guanine crystals (in bugs), yellow crystals of riboflavin (in some mammals) or white collagenous fibres. As a end result, the tapetum lucidum layer acts as a mirror.
When mild falls on the attention, it’s first incident on the retina. The mild not absorbed by the retinal cells then proceeds to the tapetum lucidum cells, which replicate it again by the rod cells to the outer layers, the place it turns into accessible as soon as once more for the retina to course of.
The web impact or profit for the animal is that the retina has two alternatives to obtain the sunshine, as soon as when it’s incident and subsequent when the tapetum lucidum sends it again. As a end result, the animal can see clearly even in darkish circumstances.
When you’re looking at, say, the cat, the glow in its eyes is the mirrored mild.
— M. Ramalingam, Coimbatore
Published – June 04, 2025 02:07 pm IST
