Image Formation

Convex Lens

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

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.

object at infinity convex lens

Fig: Object at Infinity

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


Chapter List


Object beyond C1 or 2F1
Centre of Curvature

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.

object beyond 2F convex lens

Fig: Object Beyond 2F

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

Object at C
Centre of Curvature

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.

object at 2F convex lens

Fig: Object at 2F

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


Object between C 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.

object between F2 and F convex lens

Fig: Object between 2F and F

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

Object at Focus F1

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

object at focus convex lens

Fig: Object at F

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


Between F1 and O

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.

object between F and O convex lens

Fig: Object between F and O

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

Summary of Image Formation

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


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