Images Formed by Lenses
*** इस पृष्ठ को हिंदी में पढ़े ***
Definitions
- Focal point (F) It is the point at which a beam of parallel rays converges upon or appears to diverge from. It is also known as the principal focus of the lens.
- Focal length is the distance from the centre of the lens to the focal point.
- Centre of curvature (C): It is the center of the sphere from which the lens was cut. The center of curvature for a convex lens is located on the side opposite to the object, while for a concave lens, it is located on the same side as the object.
Images formed by Convex Lens
| Position of object | Position of image | Nature of image |
|---|---|---|
| At infinity | At focus | Real, diminished, inverted |
 | ||
| At 2F | At 2F | Real, same size and inverted |
 | ||
| Between 2F and F | Beyond 2F | Real, enlarged, inverted |
 | ||
| At F | No image | Refracted rays are parallel |
| Between F and lens | On the same side as the object | Virtual, enlarged and upright |
Uses of Convex Lens
- Used in magnifying glass.
- Used to correct the vision of long-sighted persons.
Images formed by Concave Lens
| Position of object | Position of image | Nature of image |
|---|---|---|
| At infinity | At focus | Virtual, diminished, upright |
| Between infinity and F | Between the object and the lens | Virtual, diminished, upright |
Uses of Concave Lens
- Used in spy holes on doors to check the visitors.
- Used to correct the vision of short-sighted persons.
Real Images
- Real Image is an image which can be projected onto a screen.
- Real images are always located in front of the mirror and behind the lens.
- Real images are always inverted and never upright.
- Concave lenses, Convex mirrors and plane mirrors always form virtual images and can never form real images.
Virtual Images
- Virtual Image is an image which cannot be projected onto a screen.
- Virtual images are always located in behind the mirror and in front of the lens.
- Virtual images are always upright and never inverted.