The image is formed at that point where at least two refracted light rays meet ( or appear to meet ) .
Rules for convex lens :
1. Light ray incident parallel to the principal axis , meet at focus.
2. Light ray incident from focus , become parallel to the principal axis after Refraction.
3. Light ray incident on the pole of the lens passes without any deviation.
Formation of Different Types of images by a convex Lens :
Case 1. When the object is at Infinity from a convex lens , then the image formed is :
(i) At the focus,
(ii) Real and Inverted
(iii) Much smaller than the object ( or Highly Diminished).
Case 2. When the object is beyond 2f , then the image formed is :
(i) Between f and 2f on the other side of the lens.
(ii) Real and Inverted
(iii) smaller than the object ( or diminished ).
Case 3. When the object is at 2f , then the image formed is :
(i) At a distance 2f on the other side of lens.
(ii) Real and inverted
(iii) of the same size as the object.
Case 4. When the object is between f and 2f , then the image formed is :
(i) Beyond 2f.
(ii) Real and Inverted
(iii) Larger than the object ( or Magnified )
Case 5. When the object is placed at the focus of a convex lens :
(i) At infinity
(ii) Real and Inverted
(iii) Highly enlarged.
Case 6. When the object between focus and pole or optical Centre :
(i) Behind the object ( on the left side of lens )
(ii) Virtual and Eract.
(iii) Large than the object ( Enlarged or Magnified ).
Important point for convex lens :
1. A convex lens is also known as a converging lens because it converges , a parallel beam of light rays passing through it.
2. Higher the refractive index , shorter will be the focal length , similarly more the curvature, shorter is the focal length.
3. As the radius of curvature for a lens increases, its curvature decrease and, the focal length increase