why a ray of light passing through optical center of lens goes undeviated?? **need answer soon please.**

Its a part of 10 th class syllabus of chapter light .

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This only happens for one special ray. The ray that is parallel to the optical axis and goes through the center of the lens. All other rays are deviated (either in angle, displacement or both) to some extent.

I understand the definition of deviated to mean that the path is interrupted and changed. This means either in angle or displacement.

The center of a spherical lens is along the line joining the centers of curvature of the two surfaces. A ray going through these has an incident angle of zero at both surfaces and is undeviated. No other ray has this property. A ray is deviated even at a window if it does not hit the window glass normally. (The centers of curvature in this case are at infinity.)

As each concave and convex lens is supposed to be composed up of large number of small angled prisms.These prisms have angle of prism from zero at the centre & a minimum value at the edge i.e. the deviation of light varies from zero to a minimum value at the edge.so,the light goes without deviation while passing through optical centre of the lens.

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