Spherical aberration occurs because spherical surfaces are not the ideal shape for a lens but are by far the simplest shape to which glass can be ground and polished, and so are often used. Spherical aberration causes beams parallel to, but distant from, the lens axis to be focused in a slightly different place than beams close to the axis. This manifests itself as a blurring of the image.
Section-1: General Science - Physics Question - 28
The absence of electric field inside the charged conductors refers to
The absence of electric field inside the charged conductors means that electric lines of force cannot enter the empty space of any hollow conductor. Thus hollow conductor can be used to acts as an electrostatic shield. So sensitive electric instruments can be saved from external electric fields by covering them with the âhollow conductor.