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# Spherical aberration in spherical mirrors is a defect which is due to dependence of focal length ‘f’ on angle of incidence ‘ q ’ as shown in figure is given by where R is radius of curvature of mirror and q is the angle of incidence The rays which are closed to principal axis are called paraxial rays and the rays far away from principal axis are called marginal rays As a result of above dependence different rays are brought to focus at different points and the image of a point object is on a point If f_{p} and f_{m} represent the focal length of paraxial and marginal rays respectively, then correct relationship is :

- f
_{p} = f_{m}
- f
_{p} > f_{m}
- f
_{p} < f_{m}
- none of these

_{p}= f_{m}_{p}> f_{m}_{p}< f_{m}## The correct answer is: f_{p} > f_{m}

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