Page 15 - Science E-Book Prep.3 2024-2025 1st term_ unit 2_Neat

Science Department
Prep.3

Special concepts related to the lenses:

1.Center of curvature of It’s the center of the sphere where this

thelens (C): faceis a part of.

2.The optical center of It’s a point inside the lens that lies in

thelens (P): the principal axis in the mid distance

betweenits faces.

3.The radius of curvature It’s half the diameter of the sphere

ofthe face of the lens (r): wherethis face is a part of it.

4.Principal axis of the lens: It’s the straight line that joins between
the two centers of curvature of the lens

passingby the optical center of the

lens.

5.Secondary axis of the lens: It’s any line passing by the optical

center ofthe lens except the principal

axis.

6.The focus of the lens (F): It’s the point of collection of the

parallellight rays after reflection

from the lens.

7.Virtual focus of the It’s the point of collection of the

concavelens: extensionof reflected rays by a

concave lens.

8.Focal length (f): It’s the distance between the principal
focusand optical center of the lens.

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