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Concave Lens

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A lens is made up of a transparent material with two surfaces in which at one surface should be spherical in nature. Mainly there are two types of lenses, convex and concave. In each category, subdivisions are there.

According to the nature of these lenses, convex lenses are known as converging lenses and concave lenses are known as diverging lenses. The image formation of convex and concave lens is also different. This section will helps to understand the property, image formation and applications of concave lenses.  

Concave Lens Definition

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A concave lens is a kind of lens which curved inward at the center and is thickness increases along the edges. As the rays pass through the lens, each one is refracted due to the change of medium. The rays enter the lens at different angles and so they emerge from the lens at different angles.

Concave lenses cause incoming parallel rays to spread out or diverge. Since, it is known as diverging lens. The diverging rays appear to come from a single point, the focal point, on the same side of the lens as the object. The given figure shows the concave lenses.

Concave Lenses

Concave Lens Ray Diagram

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Concave lenses always cause light rays to spread out and can only form virtual images. The image is formed at the point from which the refracted rays appear to come. The image formed by a concave lens is always smaller than the object.

The ray diagrams of concave lens is given below:

1. Object is placed between O and F1

Object Between O - F

2. Object is placed at 2F1

Object at 2F1

3. Object is placed between F1 and 2F1

Object Between F1 - 2F1

4. Object placed at infinity

Object at Infinity

Position of the object
Position of the image
Nature of the image
Object is placed between O and F1
Same side; between O and F1 Virtual and erect-diminished
Object is placed at 2F1
Same side; between O and F1 Virtual and erect-diminished
Object is placed between F1 and 2F1
Same side; between O and F1 Virtual and erect-diminished
Object placed at infinity
At F1 Virtual and erect-diminished

Concave Lens Examples

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Some examples of concave lens are,
  • Concave lenses are often used in the viewfinders of cameras
  • Used in telescope as a combined lenses
  • Used as spectacles
  • It is used as door eye