Power of a concave lens is its ability to diverge light rays. Pdf optical images due to lenses and mirrors researchgate. Power of a lens is the ability of the lens to converge or diverge a ray of light incident on it. Light reflection and refraction notes for class 10.
Convex lens, optical bench, light source, target image slide, lens mounts, and screen. Determining focal lengths of concave and convex lenses. 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. Visualizing a virtual image is possible but dicult. A convex lens has 4 dioptre power having a focal length 0. Rick is observing a candle through a concave lens of focal length 8. 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. It is the reciprocal of the focal length of the lens, i. Free pdf download of cbse class 10 science chapter 10 light reflection and refraction multiple choice questions with answers. These physics lab manual may be freely downloadable and used as a reference book. Download the pdf question papers free for off line practice and view the solutions online. These 3 labs will make a great addition to your study of light and optics.
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. It will be provided by 30 september and will be updated regularly. In this experiment, we have chosen two methods to find out the focal length of a spherical lens. By knowing how lens focal length will affect the look of an image, you can choose the lens to suit that shot. Note that in step 2, the rays leaving the lens are diverging and they will not cross. A concave lens of focal length f produces an image, ncert solutions, cbse sample paper, worksheets, syllabus, notes, assignment, last year papers, ncert books. Calculate the focal length f of the concave mirror each time. If we separate a lamp housing and a screen to s cm, there must be two positions between s which can form. The procedure to find focal length of a concave mirror by uv method is given below. The distance between the pole and the principal focus of a spherical mirror is called the focal length. Physics mcqs for class 12 with answers chapter 9 ray. Determination of focal length of a converging lens and mirror.
All distances are measured from the optical centre of the mirror. 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. The focal lengths of a biconvex lens and a concave mirror are shown in figures 1 and 2, respectively. A thin convex lens can be characterized by its focal length f, the object distance, d o. The principal axis is marked off in intervals of a focal length of the lens. 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.
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. One mark questions convex mirror for seeing traffic at. Difference between convex and concave lens with figure. The distance fv is called the focal length and is commonly labeled as f. Secondly, we talk about the lens replacement method. Focal length of a concave lens is conventionally taken as negative. 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. Arrangement of components for the focal length measurement for a single lens 10.
For a diverging lens for example a concave lens, the focal. It is a lens which is thinner at the centre and thicker at the edges. Millions of thanks from depths of my heart to every subscriber and visitor. One dioptre is the power of a lens whose focal length is 1 m. Lets practice problems involving both the lens and magnification formulas in convex and concave lenses.
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. As a result, temperature at its focus increases and the substance placed at the focal point gets heated to a high temperature. 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. Concave mirror has the property to concentrate the sunlight coming from sun along with heat radiation at its focus. Students can solve ncert class 12 physics ray optics and optical instruments mcqs pdf with answers to know their preparation level. It is a diverging lens, meaning that it spreads out light rays that have been refracted through it. A convex and concave lens of focal length f are in. 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. 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. The relative deviation with respect to the obtained focal length from table w3 is 9. Which can make real images, which can cast a shadow.
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. For the same angle of incidence in media p, q and r. To determine the focal length of a spherical convex lens by lens formula method by lens replacement method. Draw the ray diagram for some parallel rays and it will be clear that, lesser the focal length greater the converging power. Apparatus an optical bench with four upright two fixed uprights in middle, two outer uprights with lateral movement, a. Continue a study of convex and concave lenses seeing how theyre alike and different. Pdf precision focallength measurement using imaging. The real image i 1 formed by the convex lens will act as the virtual object. Chapter 36 lenses a powerpoint presentation by paul e. Cbse physics lab manual for class 12 pdf download 8. To find the focal length of a concave lens using a convex. Cbse physics lab manual for class 10 pdf download 4. To find the focal length of a convex mirror using a convex lens. 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.
Focal length f is positive for converging and negative for diverging lenses. Lenses in optics applications types of lenses physics. Focal length of convex lensb11 lab report objectives of the experiment. The focal length of a convex lens is positive, while that of a concave lens is negative. A concave mirror of focal length f 1 is placed at a distance of d from a convex lens of focal length f 2. Us8903232b1 optical attachment for reducing the focal. Quiz if an object is 12 cm away from a convex lens of focal length 4 cm where will the image be. 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.
A concave lens of focal length 15 cm forms an image 10 cm from the lens. Repeat the experiment for different values of u up to 2. 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. Physics mcqs for class 12 chapter wise with answers pdf download was prepared based on latest exam pattern. To investigate the image formed by a certain thin convex lens and to determine its focal length. Sign convention is a set of rules to set signs for image distance, object distance, focal length, etc for mathematical analysis of image formation. Mcq questions for class 10 science light reflection and. The lens used above is convex and the focal length is positive. Notes for class 10 science physics chapter 10 light reflection and refraction download in pdf. 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. 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. Determines the focal length of a convex lens, when the object distance and image distance focal length of convex lens download.
It will give a virtual upright image if the object is within the focal length. A concave lens is a lens that possesses at least one surface that curves inwards. Focal length of a concave mirror and a convex lens using u. The equation that relates object distance p, image distance q and focal length f is. A convex lens gives a real, inverted image if the object is outside the focal length of the lens. By taking readings of image and object distances for different positions, a graph can be drawn. 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. Download the questions here chapter 10 class 10 light reflection and refraction. Determining the focal length of a concave mirror and the convex lens for a distant object. A beam of light coming from infinity and falling on this convex. A real object is 15 cm from a converging lens of focal length 25 cm. 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. 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.
Convex lenses, geometrical optics alevel physics tutor. Concave lenses video geometric optics khan academy. 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. Cbse physics lab manual class 10 chapters wise download here in pdf format. Introducing a concave lens results in the incoming rays from the convex lens being refracted as shown in the diagram above. Question from ncert physics class 10 chapter 10 question 034 light reflection and refraction cbse, rbse, up, mp, bihar board question text. 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. Focal length, usually represented in millimeters mm, is the basic description of a photographic lens.
At what distance from the lens a 5 cm tall object be. To find focal length of a planoconcave lens use the lens makers formula. A concave mirror of focal length f1 is placed at a. Determination of focal length of concave mirror and convex. 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. Measure the focal length from the center of the convex lens to the focal point. R1 is radius of curvature of the surface on the object side. 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. A rayzer lightbox with baseobard, two concave lenses one thick,one thin, two convex. Free pdf download of cbse physics multiple choice questions for class 12 with answers chapter 9 ray optics and optical instruments. On the contrary, the image formed by the concave lens is erect, virtual and smaller, than the object. The procedure to find focal length of a convex lens by uv method is given in ncert book. How does the focal length of a convex lens change if. Sign convention for lenses definition, examples, diagrams.1073 882 392 321 583 613 1467 631 1567 344 1475 699 1266 548 303 136 931 999 1031 1164 1147 960 356 670 1585 775 366 350 852 1148 1046 383 736 992 75 254 383 1451 609 151 1020 1287 674 1388 1274 262