Question

Long Answer Questions:
With the help of a ray diagram, explain the following terms
(a) Focus of a convex lens (b) Optical centre of a convex lens (c) Focal length of a convex lens
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Answer 1

Answer:

(a) The principal focus of a convex lens is defined as the point on which the principal axis of the light is parallel to the principal axis that converges after the refraction from the lens.

(b) The optical centre is defined as the geometric centre of the curved lens . ... Focus :The principal focus is defined as the point on the principal axis where the light rays traveling parallel to the principal axis after refraction actually meet (for a convex lens) or appear to meet (for a concave lens).

(c) The distance from the lens to the focal point is called the focal length. For converging lenses, the focal length is always positive, while diverging lenses always have negative focal lengths.