Image Formation by a Convex Lens
A convex lens can form different types of images depending on the position of the object.
Object at Infinity
The image is formed at the principal focus on the other side of the lens.
Nature: real and inverted.
Size: highly diminished.
Object Beyond 2F
The image is formed between F and 2F on the other side of the lens.
Nature: real and inverted.
Size: diminished.
Object at 2F
The image is formed at 2F on the other side of the lens.
Nature: real and inverted.
Size: same as the object.
Object Between F and 2F
The image is formed beyond 2F on the other side of the lens.
Nature: real and inverted.
Size: enlarged.
Object at F
The image is formed at infinity.
Nature: real and inverted.
Size: highly enlarged.
Object Between F and the Lens
The image is formed on the same side as the object.
Nature: virtual and erect.
Size: enlarged.
💡 Drag MN to the left or right and observe how the image changes.
Image Formation by a Concave Lens
A concave lens always forms the image on the same side as the object. The image is virtual, erect and diminished.
Image by a Concave Lens
The image is formed on the same side as the object.
The image is virtual, erect and smaller than the object.
Image Formation Rules for a Convex Lens
| Object Position | Image Position | Nature and Size |
|---|---|---|
| At infinity | At F on the other side | Real, inverted, highly diminished |
| Beyond 2F | Between F and 2F | Real, inverted, diminished |
| At 2F | At 2F | Real, inverted, same size |
| Between F and 2F | Beyond 2F | Real, inverted, enlarged |
| At F | At infinity | Real, inverted, highly enlarged |
| Between F and the lens | Same side as object | Virtual, erect, enlarged |
Quick Revision
⭐ A convex lens can form real or virtual images.
⭐ A convex lens forms a virtual image only when the object is between F and the lens.
⭐ A concave lens always forms a virtual, erect and diminished image.
⭐ Real images can be obtained on a screen.
⭐ Virtual images cannot be obtained on a screen.
Common Mistakes
| Mistake | Correct Idea |
|---|---|
| A convex lens always forms a real image. | It forms a virtual image when the object is between F and the lens. |
| A concave lens can form a real image of a real object. | A concave lens forms a virtual, erect and diminished image of a real object. |
| The image at infinity means the image does not exist. | It means the emergent rays are parallel and meet very far away. |