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# Application of Concave and Convex Lenses

Application of concave and convex lenses are an important tool to understand the application of concave and convex lenses. These are based on the two laws: - one is the law of refraction and other is the law of reflection. The main use of lenses can be used to be focusing the light in one point or light separated in different path.

A lens is an optical device which passes the refracted light, and helps in either convergence or divergence the beam of light. A simple lens consists of a single optical element. Almost all lenses are spherical lenses, in which the two surfaces are parts of the surfaces of spheres. Each of these surfaces could be either convex or concave or even planar.

Convex lens or lenses which bulge out from the lens is called convex. Concave or basically these lenses are depressed inside and hence are called concave. It is important to note that the line joining between the centers of the spheres is called axis of the lens. Mainly the concave and convex lens axis move through the lens center, because of the way lens is making. Lenses making may be cutting in ground to give them various shape and size.

The central axis may not pass through the lens physical center without any diversion. If we study about the Plano lens –convex lens, a co-liner stream of light which passes through the lens gets converged. The distance between the lenses to the spot is called focal length of the lens; the common notation of focal length is ‘f’.

Convex-concave both lenses can be either +ve or –ve focus, it is very important both concave lens and convex lens depending on the relative curvatures of both surfaces. A negative lens has a comparative concave surface and it will be thinner at the mid of the periphery. In other side, A +ve lens has a comparative convex surface and will be thicker at the mid than at the periphery.

For the application of concave and convex-lenses it is important to understand the main equation of lens which is known as Lens maker’s equation. The focal length of the lens in air can be finding the formula from the lens maker’s equation.

P= $\frac{1}{f}=(n-1)(\frac{1}{R_{1}}-\frac{1}{R_{2}})+\frac{(n-1)d}{nR_{1}.R_{2}}$

Now the basic notations of the words are as follows:-

P is denote as the power of lens

f is denoted as the focal length of the lens,

n is denoted as refractive index of the lens material,

R1 is denoted as the radius of curvature all kind of the lens. The surface very near to the light source,

R2 is denoted as the radius of curvature of all kind of lens surface very far from the light source,

This formula is very useful in understanding and finding the terms related to the concave and convex lenses. The main application of concave and convex lenses is as follows:-

1) Convex and Concave lenses are generally used in both glasses and microscopes.
2) Both of the lenses are also used in better sight.
3) They are also used in cameras also

Apart from the above applications, there are various applications as well.

Question:What would happen to the image magnification if an object is brought closer to a convex lens? A concave lens? And what are some practical applications for each type of lens? Thanks!! thanks a lot :)

Answers:Concave lenses magnify ray of light to a focus. These are used in microscopes, cameras and telescopes. If you bring the object closer to one of these, the magnification is less. Convex lenses diverge parallel light rays, giving a larger area that s visible. These are used in glasses and fish eye lenses for cameras. If you move an object closer to a convex lens, then it appears to be more of it's real size.

Question:A)Because a concave lens cannot form a real image of a real object, it is difficult to measure its focal length precisely. One method uses a second, convex, lens to produce a virtual object for the concave lens. Under the proper conditions, the concave lens will form a real image of the virtual object! A student conducting a laboratory project on concave lenses makes the following observations: When a lamp is placed 44.2 cm to the left of a particular convex lens, a real (inverted) image is formed 36.0 cm to the right of the lens. The lamp and convex lens are kept in place while a concave lens is mounted 13.4 cm to the right of the convex lens. A real image of the lamp is now formed 33.0 cm to the right of the concave lens. What is the focal length of the convex lens? B) What is the focal length of the concave lens?

Answers:the image of the first lens becomes the object of the second lens you will need a good diagram to keep track of distances in this case the first image is 36.0-13.4 = 22.6 to the right of the concave lens this is a virtual object so use -22.6 so 1/f = 1/(-22.6) + 1/33.0 I get -71.7 cm for f for the concave lens the other is easy because image and object distances are given directly

Question:Here is the website I was given with an APP that goes with the lab: http://www.physics.metu.edu.tr/~bucurgat/ntnujava/Lens/lens_e.html My questions are as follows: 1. If an object is located in font of the focal ;point of a concave mirror, how can the image size and location be described? 2. Make a generalization describing the size and approximate location of an image formed by a convex mirror regardless of the objects location? THANK YOU!

Answers:1. The image is virtual, enlarged, upright, and behind the mirror. As the object moves from the focus towards the mirror, the image moves closer to the mirror and reduces in size. Case 5 in the text, cases 7-9 in the diagram below: http://www.physicsclassroom.com/Class/refln/u13l3e.cfm 2. The image is always virtual, diminished, upright, and behind the mirror. As the object moves closer to the mirror, the image moves closer, and increases in size. http://www.physicsclassroom.com/Class/refln/u13l4c.cfm

Question:I'm doing my physics coursework about lenses. The problem is: "You are given a lens of unknown focal length F. Using your background knowledge of optical instruments, carry out an investigation to obtain suitable object and image distances for a Practical Projector." Obviously we use a convex lens for this, but can you give me a way of explaining why we use a convex lens(converging) instead of a concave lens (diverging). Also can you give me some properties of a convex lens. I do have info on this but I need as much as possible. Thanks

Answers:We've just done lenses in physics for GCSE, so i assume u r taking urs in summer too, so gd luck! Anyways, to create a projector, you need to be able to project an image on a screen (duh) so a concave lens cannot be used. A concave lens cannot create a 'real' image as the light rays do not converge on a point, as with a convex lens and to capture an image on a screen the light has to be focused to a point. However, a concave lens can create a 'virtual' image because as the light rays diverge out, if you look towards the source from the other side of the lens, the rays seem to be coming from a certain point, which is the focal point of a concave lens. (this is difficult to explain in words, so see if u can find a physics site for diagrams of lenses with light). To find a focal length of a convex lens is easy, simply set up a small light with an image in front of it and pass that through the lens, then on the other side, hold a piece of paper (or a screen if u have one) and find the point where the image is sharpest. measure the distance from the lens to the screen and that's the focal length. Hope this helps, it's hard to explain without diagrams