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NCERT Principal Focus Concave Mirror Science Chapter Class 10

Principal focus of a concave mirror

The point on the principal axis where all the rays parallel to principal.

Axis actually meet after reflection from the concave mirror.

Principal focus of convex mirror –The point on the principal where all the rays parallel to the principal axis appear to diverge reflection from convex mirror.

R=2f

Aperture

The diameter of circular outline of the reflecting surface is called aperture.

Rules for obtaining ray diagram formed by concave mirror

• A ray incident to the principal axis of a concave mirror after reflection will pass through the principal focus.


• A ray incident through the focus of a concave mirror after reflection becomes parallel to the principal axis.


• A ray passing through the centre of curvature of a concave mirror is called bock along the same path.


• A ray incident obliquely at the pole of a concave mirror is reflected obliquely by making equal angle of reflection with principal axis.