Image Formation

Convex Lens

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

• Object at Infinity
• Beyond C
• Between C and F
• Object at C
• Object at F
• Between F and O

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.

Fig: Object at Infinity

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

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.

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.

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.

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.

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.

Fig: Object between F and O

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

Summary of Image Formation