Angular Dispersion
The angle subtended between the direction of emergent violet and red rays of light from a prism is called angular dispersion .
Angular dispersion ( θ ) δ v – δ R = ( μ v – μ R ) A where δ v and δ R are angle of deviation .
Dispersive Power
W = θ / δ Y = ( μ v – μ R ) / ( μ Y – 1 )
where μ Y = ( μ v + μ R ) / 2 , is mean refractive index .
Human Eye
Human eye is an optical instrument which forms real image of the objects on retina .
Retina colours contains lakhs of cone and rod cells which of light and intensities of light respectively .
Ciliary muscles change the focal length of eye lens . This power of eye is called power of accomadation of eye .
Different defects of vision of human eye are described below
( i ) Myopia or Short-Sightedness It is a defect of eye due to which a person can see near by objects clearly but cannot see far away objects clearly .
In this defect , the far point of eye shifts from infinity to a nearer distance . This defect can be removed by using a concave lens of