Images Formed By Lenses

Have you ever noticed the watch repairer? How does he manage to locate and fix such tiny particles of the watch? What do you think does he uses to view such small parts? Yes, he uses an eyepiece that has a lens that magnifies the parts of the watch. So let us now study the types of lenses and also the images formed by lenses.

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Images Formed by Lenses

A lens is a part of a transparent thick glass which is bounded by two spherical surfaces. It is an optical device through which the rays of light converge or diverge before transmitting.

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Types of Images Formed by Lenses

Lenses are of two kinds: Convex Lenses and Concave Lenses.

Convex  Lenses

A convex lens is thicker in the middle and thinner at the edges. A convex lens is also known as a “biconvex lens” because of two spherical surfaces bulging outwards.

Images Formed By Lenses

Convex lenses include lenses that are plano-convex (i.e. these lenses are flat on one side and bulged outward on the other), and convex meniscus (i.e. these lenses are curved inward on one side and on the outer side it’s curved more strongly).

A concave lens is thicker at the edges and thinner in the middle. A concave lens is also known as a “biconcave lens” because of two spherical surfaces bulging inwards.

Concave lenses include lenses like plano-concave (i.e. these lenses are flat on one side and curved inward on the other), and concave meniscus (i.e. these lenses are curved inward on one side and on the outer side it’s curved less strongly).

Image Formation by Concave Lens

In case of the concave lens, we always get erect images, diminished images and virtual images.

Images Formed By Lenses

Object location Image location Image nature Image size
Infinity  At F2 Virtual and Erect  Highly Diminished
Beyond infinity and 0 Between F1   and Optical centre Virtual and Erect Diminished

Here if the object is very far away, the images formed by lenses will be all the more diminished.

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Images Formed By Lenses

Image Formation by Convex Lens

In case of a convex lens, if we bring the object close to the lens, the size of the image keeps on increasing. As you bring the object more close to the lens, we get the image all the more enlarged. So here we can say that the images formed can be of a variety of types. We can have diminished inverted image, small sizes inverted image, enlarged inverted image, enlarged erect image. So in a concave lens, there is a possibility of getting a real as well as an inverted image.

Object location Image location Image nature Image size
Infinity  At F2 Real and Inverted Diminished
Beyond 2F1 Between 2F2   and F2 Real and Inverted Diminished
Between 2Fand F1  Beyond 2F2 Real and Inverted Enlarged
 At F1  At infinity Real and Inverted Enlarged
At 2 F1 At 2F2 Real and Inverted  Same size
Between Fand 0 On the same side as object Virtual  and Erect Enlarged

Images Formed in Different Lenses

Images Formed By Lenses

Which lens would you use as a magnifying glass?

Images Formed By Lenses

Looking at the image what do you think? What kind of image is formed? Yes, an enlarged image is formed. We cannot get such image using a concave lens because the concave lens always produces the diminished image. So this is a convex lens.

Images through lenses as real, virtual, erect or magnified

Images Formed By Lenses

The figure shows the virtual image formed by the convex lens and real image formed by a concave lens.

Learn more about the Different type of Mirrors here.

Solved Examples for You

Question. How should people wearing spectacles work with a microscope?

  1. Should keep wearing their spectacles
  2. They should never use the microscope
  3. Should take off their spectacles
  4. They should either keep wearing their spectacles or take off their spectacles.

Solution: Option C. If operator using microscope usually wears spectacles for working at their PC’ s, they often need to remove them while looking through the microscope so they can align their eyes correctly.

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