Page 25 - Science E-Book Prep.3 2024-2025 1st term_ unit 2_Neat

Science Department
Prep.3

Give reasons:

1- No image is formed in the focus of convex lens.

Because the penetrating rays pass parallel at infinity.

2- The long-sightedness is treated by a suitable convex lens
Because the convex lens collects the rays, to form the image exactly on the
retina.

3- The lens has two centers of curvature. (c1, c2 )
Because it has two spherical surfaces, each surface has a center.

4- The shorted sighted person.
Due to: 1) increase in the eye ball diameter.
2) increase in the convexity of the eye lens surface.

5-The short-sightedness is treated by using a concave lens.
Because it diverges light rays to form an image exactly on the retina.

6- The lens has two foci but the spherical mirror has one focus only.
Because the lens is a part of two spherical surfaces while the spherical
mirror is a part of one sphere.

First Term 43