Class 10 Science


Light: Image Formation by Convex Lens

These notes are based on the chapter Light: Reflection and Refraction from class 10 science NCERT book and CBSE syllabus

There are six possibilities of position of object in the case of convex lens:

  1. Object at Infinity
  2. Beyond C
  3. Between C and F
  4. Object at C
  5. Object at F
  6. Between F and O

Object at infinity

object at infinity convex lens

Fig: Object at Infinity

Convex lens converge parallel rays coming from objet at infinity and a highly diminished - point sized, real and inverted image is formed at principal focus F2.

Properties of Image: Image is highly diminished, real and inverted.

Object beyond C1 or 2F1

object beyond 2F convex lens

Fig: Object Beyond 2F

A diminished, real and inverted image is formed between principal focus, F2 and centre of curvature, C2 at the opposite side when an object is placed beyond C1 of a convex lens.

Properties of Image: Image is diminished, real and inverted.

Object at C or 2F1

object at 2F convex lens

Fig: Object at 2F

A same sized, real and inverted image is formed at centre of curvature, C2 when object is placed at centre of curvature, C1 of a convex lens.

Properties of Image: Image is same size as object, real and inverted.

Object between C and F

object between F2 and F convex lens

Fig: Object between 2F and F

An enlarged, real and inverted image is formed beyond centre of curvature, C2 when an object is placed between centre of curvature, C1 and principal focus, F1 of a convex lens.

Properties of Image: Image is enlarged, real and inverted.

Object at Focus F1

object at focus convex lens

Fig: Object at F

An infinitely large, real and inverted image is formed at infinity when object is placed at principal focus, F1 of a convex lens.

Properties of Image: Image is highly enlarged, real and inverted.

Between F1 and O

object between F and O convex lens

Fig: Object between F and O

Properties of Image: Image is enlarged, virtual and erect.

A virtual, erect and enlarged image is formed at the same side of lens, when an object is placed between principal focus, F1 and optical centre, O of a convex lens.

Summary of Image Formation

  • Object at Infinity: Image is formed at focus. Image is real, inverted and highly diminished in size.
  • Beyond C: Image is formed between F2 and 2F2. Image is real, inverted and smaller than object.
  • Between C and F: Image is formed beyond C2 or 2F2. Image is real, inverted and larger than object.
  • At C: Image is formed at 2F2 or C2. Image is real, inverted and of same size as object.
  • At F: Image is formed at infinity. Image is real, inverted and highly enlarged.
  • Between F and O: Image is formed on 2F1. Image is virtual, erect and larger than object.

More from this Lesson