As per Young-Helmholtz theory colour revealing are of_____ types

Ans. b (3) (Ref. Parsons, Disease of Eye, 19th/131; Khurana, Ophthalmology, 3rd/250; Ganong, Physiology, 21/166)# Normal color vision is trichromatic, the basis of Young-Helmholtz theory of colour vision.YOUNG-HELMHOLTZ THEORY# Cones are photoreceptors tightly packed in fovea centralis where there are no rods and other layers of retina very thin.# The central part of fovea consists of cones and their nuclei largely and all other retinal layers are absent.# The appreciation of colors is function of cones and occurs in photopic vision.# Sensation of any colour is determined by the relative frequency of impulses for cone system.# Normal color vision is trichromatic, the basis of Young-Helmholtz theory of colour vision.# Other theories of color vision are- Hering or Hurvich and James Law (trichromatic signal from cones fed into subsequent neural stage and exhibit spectral opponent and spectral non-opponent property), and- Edwin-Land wavelength theory.