Question

Describe the source of distortion and the means of correction in terms of the wave model of light and wave optics. Be sure to use the terms ray, wave, reflection, refraction and focal point in your response.

Answer 1

Distortions are defects in images formed by lens.

Distrotions are mainly two types 1) Geometrical Distortions 2) chromatic distortions

Geometric Distortions are mainly due to shape of the lens. one important distortion is Spherical distortion. Spherical Distortion causes due to the position of incident ray striking the lens.

Those rays which are striking nearer to principal axis, deviate less and have a focal point far away from lens compared with the rays striking the lens at height far from principal axis. these rays deviate less and have a focal length less. hence the image will be a curved image for a straight object. the distortion is called spherical distortion.

Chromatic Distortion: This arises due the material of lens. The refractive index of material of a lens depends on wave length. hence for red color wave length is more and for violet its less.

refractive index is less for red color, for violet it is more. for a thin lens focal length depends on refractive index as well as its curvature.

for red color focal length is less and for violet focal length of lens is more. different colors form the different images at different focal points causes color images for white object called chromatic distortion