Focal length of a concave mirror and a convex lens using u. It is a diverging lens, meaning that it spreads out light rays that have been refracted through it. A convex lens is also known as the converging lens as the light rays bend inwards and converge at a point which is known as focal length. On the contrary, the image formed by the concave lens is erect, virtual and smaller, than the object. In this experiment, we have chosen two methods to find out the focal length of a spherical lens. A convex lens gives a real, inverted image if the object is outside the focal length of the lens. Sign convention for lenses definition, examples, diagrams.
Quiz if an object is 12 cm away from a convex lens of focal length 4 cm where will the image be. Lets practice problems involving both the lens and magnification formulas in convex and concave lenses. Introducing a concave lens results in the incoming rays from the convex lens being refracted as shown in the diagram above. It will give a virtual upright image if the object is within the focal length. The focal length of a convex lens is positive, while that of a concave lens is negative. While both of the other responses are theoretically correct, there is a small assumption that has been made that the lenses used are thin lenses with no influence coming from the thickness of the lens. All distances are measured from the optical centre of the mirror. For the same angle of incidence in media p, q and r. The procedure to find focal length of a concave mirror by uv method is given below. For an object kept at a distance of 6 0 c m from the convex lens, the final image, formed by the combination, is a real image, at a distance of. If we separate a lamp housing and a screen to s cm, there must be two positions between s which can form. A concave mirror of focal length f 1 is placed at a distance of d from a convex lens of focal length f 2. Free pdf download of cbse class 10 science chapter 10 light reflection and refraction multiple choice questions with answers.
Secondly, we talk about the lens replacement method. Note that in step 2, the rays leaving the lens are diverging and they will not cross. Generally, a convex lens forms a real image, but it can also create a virtual image when the object is in the middle of the focus and optical centre. At what distance from the lens a 5 cm tall object be. Notes for class 10 science physics chapter 10 light reflection and refraction download in pdf.
A convex lens has 4 dioptre power having a focal length 0. Students can solve ncert class 12 physics ray optics and optical instruments mcqs pdf with answers to know their preparation level. How does the focal length of a convex lens change if. Question from ncert physics class 10 chapter 10 question 034 light reflection and refraction cbse, rbse, up, mp, bihar board question text. If the concave lens was not there and the object was at a distance greater that its focal length the convex lens would form a real image. To find focal length of a planoconcave lens use the lens makers formula. A concave lens of focal length 15 cm forms an image 10 cm from the lens. One mark questions convex mirror for seeing traffic at. A thin convex lens can be characterized by its focal length f, the object distance, d o. Convex lens, optical bench, light source, target image slide, lens mounts, and screen.
Pdf precision focallength measurement using imaging. Calculate the focal length f of the concave mirror each time. Apparatus an optical bench with four upright two fixed uprights in middle, two outer uprights with lateral movement, a. Focal length of a concave lens is conventionally taken as negative. It is not a measurement of the actual length of a lens, but a calculation of an optical distance from the point where light rays converge to form a sharp image of an object to the digital sensor or 35mm film at the focal plane in the camera. To investigate the image formed by a certain thin convex lens and to determine its focal length. By taking readings of image and object distances for different positions, a graph can be drawn. It is a lens which is thinner at the centre and thicker at the edges. A convex lens, of focal length 3 0 c m, a concave lens of focal length 1 2 0 c m, and a plane mirror are arranged as shown. Focal length f is positive for converging and negative for diverging lenses. The distance between the pole and the principal focus of a spherical mirror is called the focal length.
For a converging lens for example a convex lens, the focal length is positive, and is the distance at which a beam of collimated light will be focused to a single spot. Mcq questions for class 10 science light reflection and. The principal axis is marked off in intervals of a focal length of the lens. Sign convention is a set of rules to set signs for image distance, object distance, focal length, etc for mathematical analysis of image formation. The equation that relates object distance p, image distance q and focal length f is. So just remember, concave has the word cave in it so i always imagine that its kind of caving inwards caving inwards its a little bit of an exaggerated drawing but you get. To find the focal length of a concave lens using a convex lens physics lab manualncert solutions class 12 physics sample papers aim to find the focal length of a concave lens using a convex lens. An optical attachment having five or six elements and configured to be operably arranged on the image side of an objective lens to reduce the focal length and focal ratio of the objective lens is disclosed. A real object is 15 cm from a converging lens of focal length 25 cm. Focal length is defined as the distance between the center of the lens or mirror and the focal point of the lens or the mirror. It can be observed that the value calculated was exactly equal to the theoretical focal length of the concave lens, making the experimental value of the focal length of the concave lens in table w4 valid.
For a diverging lens for example a concave lens, the focal. When a concave lens of focal length f 2 is placed coaxially in contact with a convex lens of focal length f 1 and if f is the focal length of the combination, then, therefore, the focal length of the concave lens, b lens out of contact method. A convex and concave lens of focal length f are in. It is the reciprocal of the focal length of the lens, i. Cbse physics lab manual class 10 chapters wise download here in pdf format. On the other hand, the concave lens is also known as a diverging lens because it bends the parallel light rays outward and diverges them at the focal point. Focal length, usually represented in millimeters mm, is the basic description of a photographic lens. It will be provided by 30 september and will be updated regularly. One dioptre is the power of a lens whose focal length is 1 m.
Convex lenses, geometrical optics alevel physics tutor. R1 is radius of curvature of the surface on the object side. Power of a concave lens is its ability to diverge light rays. The lens used above is convex and the focal length is positive. A concave mirror of focal length f1 is placed at a. Concave lenses video geometric optics khan academy. Arrangement of components for the focal length measurement for a single lens 10. Lenses in optics applications types of lenses physics.
Us8903232b1 optical attachment for reducing the focal. A concave lens of focal length f produces an image, ncert solutions, cbse sample paper, worksheets, syllabus, notes, assignment, last year papers, ncert books. The focal length f of a lens can be found quite accurately by moving an illuminated object infront of a lens so that an image is cast on a screen. To find the focal length of a concave lens using a convex. Determination of focal length of concave mirror and convex. For a thin lens in air, the distance from the lens to the spot is the focal length of the lens, which is commonly represented by f in diagrams and equations. These physics lab manual may be freely downloadable and used as a reference book. Determining focal lengths of concave and convex lenses. Chapter 36 lenses a powerpoint presentation by paul e. The real image i 1 formed by the convex lens will act as the virtual object. A beam of light coming from infinity and falling on this convex.
Continue a study of convex and concave lenses seeing how theyre alike and different. Download the questions here chapter 10 class 10 light reflection and refraction. Free pdf download of cbse physics multiple choice questions for class 12 with answers chapter 9 ray optics and optical instruments. The focal lengths of a biconvex lens and a concave mirror are shown in figures 1 and 2, respectively. A rayzer lightbox with baseobard, two concave lenses one thick,one thin, two convex. Rick is observing a candle through a concave lens of focal length 8.
For a thin lens in air, the focal length is the distance from the center of the lens to the principal foci or focal points of the lens. Download the pdf question papers free for off line practice and view the solutions online. In this section of the experiment, we will use two lenses to form a real image of the virtual image from a concave negative focal length lens. Millions of thanks from depths of my heart to every subscriber and visitor. The procedure to find focal length of a convex lens by uv method is given in ncert book. To find the focal length of a convex mirror using a convex lens. Cbse physics lab manual for class 12 pdf download 8. Pdf optical images due to lenses and mirrors researchgate. Measure the focal length from the center of the convex lens to the focal point. Which can make real images, which can cast a shadow.
Power of a lens is the ability of the lens to converge or diverge a ray of light incident on it. The relative deviation with respect to the obtained focal length from table w3 is 9. Physics mcqs for class 12 with answers chapter 9 ray. An extended hemispherical lens is a special type of planoconvex lens, in which the lenss curved surface is a full hemisphere and the lens is much thicker than the radius of curvature. These 3 labs will make a great addition to your study of light and optics. A concave lens is a lens that possesses at least one surface that curves inwards. Focal length of convex lensb11 lab report objectives of the experiment. Repeat the experiment for different values of u up to 2. Physics mcqs for class 12 chapter wise with answers pdf download was prepared based on latest exam pattern. The optical attachment is particularly suitable for adapting objective lenses designed with a relatively large working distance for a large format size to cameras having a smaller format. The distance fv is called the focal length and is commonly labeled as f. One characteristic feature of all thin lenses and concave mirrors is the focal length, f, and is defined as the image distance of an object that is positioned infinitely far way.
To determine the focal length of a spherical convex lens by lens formula method by lens replacement method. Light reflection and refraction notes for class 10. Difference between convex and concave lens with figure. Weve talked a lot about convex lenses, so i thought i would do a quick video on concave lenses, although there arent as many combinations of what a concave lens can do. Cbse physics lab manual for class 10 pdf download 4. Visualizing a virtual image is possible but dicult. Extra question 3 marks question 2 an object is placed at a distance of 60 cm from a concave lens of focal length 30 cm i use lens formula to find the distance of the image from.
961 1085 509 701 1182 1311 1522 1307 1607 808 976 527 513 1368 1163 1361 1095 571 683 1371 380 1042 438 1207 738 1638 644 354 115 51 847 1408 1027 278 1293 154 1382 1282 599 1351 173 1187 1216 124 871 936