Question

Which one is the correct difference between rod and cone cells?

		Rod cells	Cone cells
(A)	Overall function	Vision in poor light	Colour vision and detailed vision in bright light.
(B)	Distribution	More concentrated in centre of retina	Evenly distributed all over the retina.
(C)	Visual activity	High	Low
(D)	Visual pigment	Iodopsin	Rhodopsin

Answer 1

Hint: The inner coat of the eyeball is the retina. It contains the actual light receptors, the rods and cones, and thus retina functions in the same way as the film of a camera does. Retina contains three layers of cells- from inside to outside-ganglion cells, bipolar cells and photoreceptor cells. There are two types of photoreceptor cells, namely, rods and cones. These cells contain the light-sensitive proteins called the photopigments.

Complete answer:

	Rod cells	Cone cells
Number of cells	They are more in number	They are less in number
Pigment present	They have rhodopsin in them	They have Iodopsin in them
Type of vision	They give response to dim light that is give vision in poor light	They give detailed and colour vision and operated in bright light
Distribution	They are distributed at periphery of retina	They are distributed at centre of retina
Speed of response to light (visual activity)	They give slow response (low)	They give fast response (high)
Size	They are small	They are large
Number of visual pigment	Only one pigment is present	Three visual pigments are present.

According to above mentioned differences the correct option is a) that rod cells function is vision in poor light and cones colour vision and detailed vision in bright light.

Note: The visual pigments for colour vision are: erythrosine (sensitive to red), chloropsin (sensitive to green) and cyanopsin (sensitive to blue). In moonlight we cannot see colors because only the rods are functioning. Due to the low light level cones are not functioning, And the sensations of different colours are produced by various combinations of these cones and their photopigments. When these cones are stimulated equally, a sensation of white light is produced.