what is concave and convex lens
Answers
Convex lenses are thicker at the middle. Rays of light that pass through the lens are brought closer together (they converge). A convex lens is a converging lens.
When parallel rays of light pass through a convex lens, the refracted rays converge at the focal point. The image formed is magnified (you can use this lens as a magnifier, or a simple camera lens by itself). It’s also called “positive” lens.
Concave lenses are thinner at the middle. Rays of light that pass through the lens are spread out (they diverge). A concave lens is a diverging lens.
When parallel rays of light pass through a concave lens the refracted rays diverge so that they appear to come from one point called the principal focus. The image formed is diminished. It’s also called “negative” lens. This lens can’t be used to form an image by itself, but in combination(s) with positive (converging) lenses it is used to shorten the focal length.
This is just a basic, simple answer to your question. There are many types or shapes of concave / convex lenses (including their combinations) and I could easily go on for a week about optics :-D
CONCAVE LENS :------------
Unlike a convex lens the nature and general position of the image formed by a concave lens does not depend upon the distance of the object from the lens . A concave lens always form of virtual , erect and diminished image. Also, the image always appears to be located between the optical centre and the 'F' point of lens on the same side as the object is . We illustrate these pictures of the concave lens by drawing Ray diagrams for three different distances of the object from the lens .
In all cases the image formed is virtual , erect and diminished one. Also, it always appears to be formed between the optical centre and the 'F' point of the lens .
CONVEX LENS :--------------
A concave lens forms image of different size , nature , and at different positions for objects kept at different distances from its optical centre . We consider the following 6 cases that cover all possible types of images formed by this lens . The characteristics of the image formed have been written --------»
★ OBJECT AT INFININTY :------------
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The image of very far object (object at infinity ) is a real,diminished and almost point - Like image. It is formed at the focus of the lens .
★ OBJECT (SOMEWHAT) BEYOND THE '2F' POINT OF THE LENS :--------------
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The image formed here is a real , diminished and inverted image. It is formed between the 'F' and '2F' points of the lens , on its other side ( the side opposite to the side on which the object has been put ')
★ OBJECT AT THE '2F' POINT OF THE LENS :-------------
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The image formed year is real and inverted image that has the same size as the object. It is formed at '2F' point of the lens on the other side of the lens .
★ OBJECT BETWEEN THE '2F' AND 'F' POINTS OF THE LENS :------------
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The image formed here is real , inverted and magnified image . It is formed beyond the '2F' point of the lens on its other side.
★ OBJECT KEPT AT THE (FIRST) PRINCIPAL FOCUS OR THE 'F' POINT OF THE LENS :-----------------
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The image formed here is regarded as a real , inverted and magnified image . It is regarded as formed 'very far off' or at infinity.
