Question

Which of the following statements is incorrect about cones?
(i) The daylight vision and colour vision are functions of cones.
(ii) In the human eye, there are three types of cones having characteristic photopigments that respond to red, green and blue light.
(iii) The sensations of different colours are produced by various combinations of these 3 types of cones.
(iv) When these 3 types of cones are stimulated equally, a sensation of white light is produced.

A. Only (iv)
B. Only (i) and (iv)
C. Only (iii)
D. none of these

Answer 1

Hint: Human eyes consist of majorly two receptors: Rods and Cones. Cone cells present in the retina(especially in the central fovea) are photoreceptor cells. These help in vision and colour sensitivity.

Complete Step by Step Answer:
Cones are specifically efficient in bright light. Although, their sensitivity is less intense than that of rods. Rods require less light for sensitization.
In the human eye, there are three types of cones having characteristic photopigments that respond to red, green and blue light. It can also be said that they respond to three types of wavelength: long wavelength (red), medium wavelength (green), short wavelength (blue).

When these 3 types of cones are stimulated equally, a sensation of white light is produced due the additive effect of these colours’ wavelength.

Thus, the correct answer is D: none of these.

Note: Rods are responsible for scoptic or twilight vision while cones are responsible for photopic vision. The ratio of rods:cones is 20:1. Unlike cones, rods do not help in colour differentiation.