Question

Define Braille, cone cell and rod cell.

Answer 1

a form of written language for blind people, in which characters are represented by patterns of raised dots that are felt with the fingertips.
Cone cells, or cones, are one of three types of photoreceptor cells in the retina of mammalian eyes (e.g. the human eye). They are responsible for color vision and function best in relatively bright light, as opposed to rod cells, which work better in dim light. Cone cells are densely packed in the fovea centralis, a 0.3 mm diameter rod-free area with very thin, densely packed cones which quickly reduce in number towards the periphery of the retina. There are about six to seven million cones in a human eye and are most concentrated towards the macula.^[1] The commonly cited figure of six million cone cells in the human eye was found by Osterberg in 1935

Rod cells are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor, cone cells. Rods are usually found concentrated at the outer edges of the retina and are used in peripheral vision. On average, there are approximately 90 million rod cells in the human retina.^[1] Rod cells are more sensitive than cone cells and are almost entirely responsible for night vision. However, rods have little role in color vision, which is one of the main reasons why colors are much less apparent in darkness.