Lets first consider a double convex lens shown in figure 21. The aim of this package is to provide a short self assessment programme for students. These equations, called the thin lens equation and the lens makers equation, allow us to quantitatively analyze thin lenses. Rays of light from an object very far away from a thin lens will be approximately parallel. Consider a converging lens for which the object is outside the focal point. The light rays will then refract as they pass through the lens and, for a converging lens, form an image at a distance d i refer to fig. A convex lens is thicker in the center than at the edges and can also be called a positive lens or converging lens. When the parallel rays of light pass through a convex lens, the refracted rays converge at a single point called the principal focus. The purpose of this lab is to introduce students to some of the properties of thin lenses and mirrors. The glass lens which is thicker at its center than its edge is the converging lens. Lenses whose thickness is not negligible are sometimes called thick lenses the thin lens approximation ignores optical effects due to the thickness of lenses and simplifies ray tracing calculations.
In optics, a thin lens is a lens with a thickness distance along the optical axis between the two surfaces of the lens that is negligible compared to the radii of curvature of the lens surfaces. The nickels image has twice the diameter of the nickel when the lens is 2. Nov 22, 2016 smu department of physics smu dedman college of humanites. The camera uses a converging lens whose focal length is 0. Conform with the policy on written homework solutions. General physics ii experiment 8 spherical lenses i. Each point of a selfluminous object or reflection object o is a source of light with a. For the case drawn in the figure, light ray 1 is parallel to the optical axis, so the outgoing ray is bent once at the center of the lens and goes through the focal point. Remove the lenses from the lens holders and place them in the plastic tray provided. General physics ii course lecture notes section xii. A diverging concave, negative lens normally forms a virtual image that can not be projected on a screen.
The purpose of this lab was to study objectimage relationships by observing the characteristics such as magnification and orientation of real and virtual images formed by a thin lens using an optics bench and a light source. For a thin lens, d is much smaller than one of the radii of curvature either r 1 or r 2. The physics of lenses is also used to detect the presence of dark. Remove lens d from the bench, leaving lens a in place at the 50 cm mark. Click the button below to download the full physics form 4 notes pdf. Free physics revision notes on thin converging lens. A correlation of thin lens approximation to thick lens design. These are known as thin lenses and the equations we introduce are limited to such lenses. Scribd is the worlds largest social reading and publishing site.
This laboratory will be performed in the discovery format. Show that in the figure opposite the lenses in the left column are convex positive f whereas the lenses in the right column are concave negative f. Thin converging lens cie igcse physics revision notes. Image formation by mirrors and lenses physics courses. Focal lengths of converging lenses from the thin lens equations, if the object distance p is very large p. A very commonly used optical device is the thin lens. If the object is in front of the lens, the object distance is positive.
Lab 10 board notes thin lenses friday, may 30, 2014 9. How far is the lens from the slide if the image is a real. Thin lenses a very commonly used optical device is the thin lens. The thin lens equation and the magnification equation example. From last weeks lab, reflection and refraction, you should already be familiar with the following terms. In these conditions, the last term of the lensmakers equation becomes negligible, and the focal length of a thin lens in air can be. Convex lenses focus distant images at a point on the side of the lens opposite from a light source. Thin lenses conclusion conclusion thin lenses are optical. Pdf graphing 1o versus 1i is a valuable exercise for students to verify the thin lens equation. Lab 4 thin lenses experimental goals chapter 6 of the lab reference manual discusses the basic principles of thin lens optics. The basics of lenses in combination are the image of an object from one lens becomes the object for the second lens.
Physics in the arts, revised edition c 2012 elsevier inc. Designed by the teachers at save my exams for the cie igcse physics 0625 0972 syllabus. Firstly, we talk about the theory of the first method. Smu department of physics smu dedman college of humanites. Glu logistics command, technical management department, 06110 g. A convex lens left has a positive focal length, a concave lens right has a negative focal length. The application of the thin lens equation and the magni.
Nearby object as mentioned, a diverging lens will usually form a. Converging lenses the approximate focal length of a thin converging lens is the distance from the lens to a screen on which is formed the real image of a very distant object, such as the landscape seen through a window of the laboratory. Note that the lens makers formula works only for thin lenseslenses for which the thickness is. Lab 4 thin lenses physics and astronomy department. The image must be real, so you choose to use a converging lens. If light is incident from the left as will be considered in most of the questions and sketches the signs of spherical surfaces are as follows. Solution solve the thin lens for the focal length and insert the desired object and. Thin lenses 127 rays of light from a nearby object will arrive at the lens at various angles. Incident rays parallel to the optic axis will be bent by refraction at both surfaces of the lens toward the optic axis figure 21. To study and verify some of the laws of optics applicable to thin lenses by determining the focal lengths of three such lenses two convex, one concave by several methods. Solving problems involving thin lenses and images smu physics. State at least two possible physics sources of our percent error do not i. The primary goals are to understand the relationship between. A correlation of thin lens approximation to thick lens design by using coddington factors in lens design and manufacturing o.
If an object is placed a distance, p, that is much farther than the focal length of a lens, f i. Mirrors and lenses east tennessee state university. These distances and focal lengths are related by the thin lens equation. They are lens formula method and lens replacement method. The primary goals are to understand the relationship between image distance, object distance, and image scale. A lens that causes light rays to bend toward away from its optical axis is a. A lens is considered to be thin if its thickness t is much less than the radii of curvature of both surfaces, as shown in figure 2. Lecture 18 geometric optics ii thin lenses unm physics and. Concave lenses focus distant objects so someone on the. Free notes types of thin lenses images formed by thin lenses. Phy 112l activity 10 university of southern mississippi. This handout is provided as a guide to the equipment and possible measurements but students are encouraged to develop their own. For a thin lens there is a common point, the focal.
Image formation by mirrors illustrate image formation in a flat mirror. An important property of a lens is its focal length, f. A thin lens is one whose thickness is negligible in comparison to the image and object distance. In this experiment, the formation of images by concave and convex lenses will be explored. If p is not infinite but still large compared to the focal length i. Thin lenses and optical instruments equipment 1 meter optical bench with 5 moveable mounts, lighted test object, 3 lens holders, screen, 2 short focal length double convex lenses l1, e1, 2 medium focal length double convex lenses l2 and l3, 1 long focal length double convex lens l4, 1 double concave lens l5. Images with thin lenses washington state university. The student will measure the focal lengths of two converging lenses and, for the proper choice of object distances, will measure image distances and study the nature of the. In particular, the last section leads you partway through the derivation of a simple relationship called the thin lens equation between the object distance p, the image distance q, and the focal length f of a convex.
This handout is provided as a guide to the equipment and possible measurements but students are encouraged to develop their own techniques for exploring the phenomena and presenting results. The formula relating these quantities is the thin lens equation. Consider the thick biconvex lens shown in figure \\pageindex8\. Phys ii converging lenses imaging introduction and theory. The thinlens equation and the magnification equation f dd i o. Lawrence university physics 104 slu physics thin lenses department of physics revised. Practically speaking, it means we trace the rays to the center plane of the lens and then refract them for both surfaces. Thin lenses, converging lens, diverging lens, lens equation, object. The objective of this experiment was to measure the focal.
The sign of the image distance can tell you additional information on the image. The angular magnification of a telescope is given by m f1 f2, so it makes sense to have a large f1 and a small f2. Illustrate the formation of images using the technique of ray tracking. Lenses are used in making spectacles, cameras, cinema projectors, microscopes and telescopes. All lenses have 2 focal points, one on each side of the lens, but only one focal length. Again the object and image distances having opposite signs. Image formation by lenses list the rules for ray tracking for thin lenses. The focal length, f, is positive for converging lenses and negative for diverging lenses. For an object height, y o, and an image height, y i, the magnification, m, is given by o i o i s s y y. In this case, the rays may be considered to bend once at the center of the lens. A lens which is thicker at its edges than at its centre diverges light and is known as concave or diverging lens.
Determine the combined strength of a thin convex lens. Just as we had for mirrors, the thin lens equation is. A ray parallel to the lens axis passes through the far focus of a converging lens or appears to come from the near focus of a diverging lens. The focal length of a lens depends on the refractive index of the material of the lens n l, the refractive index of the medium in which it is immersed n m and the radii of curvature of the two faces of the lens r 1 and r 2 according to the formula valid for thin lenses. Using the thin lens equation requires the following sign conventions. Objective the objective of this experiment is the study of the image formation properties of spherical thin lenses. The application of the thin lens equation and the magnification. Using the thin lens equation, and the information that the image distance is 5cm. Thin lenses cal state fullerton, department of physics.
A concave lens is thinner at the center than at the edges and can also be called a negative lens or a diverging lens. The term thin is, of course, qualitative, and just means in this sense that we can ignore the thickness of the lens when ray tracing. General physics ii austin community college district. Thin converging lenses free download as powerpoint presentation. Practically speaking, it means we trace the rays to the center plane of the lens. The term thin is, of course, qualitative, and just means in this sense that we can ignore. However, if the focal length of the second lens is longer. A lens which is thicker at its centre than at its edges converges light and is called convex or converging lens. This handout is provided as a guide to the equipment and possible measurements but students are encouraged to develop. Place the screen back on the bench, close to the lens and on the side of the lens opposite the window. The image forms at the focal length when the object is in.
F o object height h final image f e eyepiece image formed by objective lens is inside focal length of eyepiece lens. Thin lenses physics 227 lab variables relate to the diagram. Conclusion thin lenses are optical devices manufactured in ways that bend light in various different ways. The focal length can be found by using the thin lens equation and solving for the focal length. Phys ii converging lenses imaging introduction and.
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