Center of curvature: - The reflecting surface of a spherical mirror forms a part of a sphere. Nature, position and relative size of the image formed by a convex mirror is given below in the table. The magnification produced by a lens is defined as the ratio of the height of the image and the height of the object. The incident ray, the reflected ray and the normal to the mirror at the point of incidence all lie in the same plane. It is represented by the letter R. Pole: - The center of a spherical mirror is called its pole and is represented by letter P as can be seen in figure 2. A ray of light parallel to the principle axis of a convex mirror appears to be coming from its focus after reflection from the mirror. Sign Convention for Spherical Lenses. \$\angle RQ{{N}_{2}}=\angle QR{{N}_{3}}=r\$ and is called angle of refraction. Refraction is due to change in the speed of light as it enters from one transparent medium to another. The object is always placed to the left of the mirror. Relationship between focal length, image distance and object distance for spherical mirrors - result The figure shows an object AB at a distance u from the pole of a concave mirror. It is represented by the letter C. Please note that the center of curvature is not a part of the mirror. The refraction of light takes place on going from one medium to another because the speed of light is different in two media. Power of a convex lens is positive and that of a concave lens is negative. We can see the sign convention in both mirrors Some points to note Since focus of concave mirror is on the left side (in front of the mirror) , Focal length of concave mirror is negative Since focus of convex mirror is on the right side (behind the mirror), Focal length of convex mirror is positive When light ray is made to travel from one medium to another say from air to glass medium then light rays bend at the boundary between the two mediums. Aperture of the mirror actually represents the size of the mirror. (iii) The distances measured against the direction of incident light are taken as negative. You can use above books for extra knowledge and practicing different questions. However, it lies behind the mirror in case of a convex mirror as shown above in the figure 2. Practice: Using magnification formula for lenses. The center of curvature of a concave mirror lies in front of it. So, the bending of light when it passes from one medium to another is called. An image is formed when the light rays coming from an object meet at a point after reflection from a mirror (or refraction from lens). The distance of the principal focus from the optical centre of a lens is called its focal length represented by letter f . If we now observe the reflected rays we see that they are all intersecting at a point F on the principal axis of the mirror. A lens has two principal foci. In this convention, the pole (P) of the mirror is taken as the origin. From figure 3a we see that a number of rays parallel to the principal axis are falling on a concave mirror. A ray of light through the optical centre of a lens passes without suffering any deviation. 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Commonly used terms about Spherical mirrors :-. Sign convention for lens is similar to that of spherical mirror. Lens Formula gives the relationship between object distance (u), image image-distance (v) and the focal length (f ) and is expressed as. Thin lens formula . Refer to the diagram for clear visualization. Convex mirrors are used as rear view mirrors in automobiles to see the traffic at back side as they give erect images and also highly diminished one giving the wide field view of traffic behind. The image is either magnified, reduced or has the same size, depending on the position of the object. This sphere has a center. When light falls on the surface of an object it can either be, Absorbed:- If an object absorbs all the light falling on it , then it will appear perfectly black for example a blackboard. The sign is taken as positive (+) above the origin point at Y-axis; and below the origin point as negative (-) at Y-axis. The type of image formed by a concave mirror depends on the position of the object kept in front of the mirror. Mirrors we use on our dressing tables in our home are plane mirrors. PLEASE READ MY DISCLOSURE FOR MORE INFO. Reflected:- If an object sends back light rays falling on its surface then it is said to have reflected the light, The process of sending back light rays which falls on the surface of an object is called. This implies that the light from the object falls on the mirror from the left-hand side. Following sign convention is used for measuring various distances during the formation of images by lenses: All distances on the principal axis are measured from the optical center. We can place the object at following places, Between focus F and center of curvature C, At far off distances called infinity and cannot be shown in the figures, Image formation by a concave mirror for different positions of the object is shown below in the table. Note: Sign convention can be reversed and will still give the correct results. A concave lens bulges inward and is thinner in the middle and thicker at the edges. Magnification produced by a lens is also related to the object-distance u, and the image-distance v and is given by, The power of a lens is defined as the reciprocal of its focal length. The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane. Now a question arises what happens when light travels from one medium to another with different densities for example from air to glass. Lakhmir Singh, Together with CBSE/NCERT Practice Material Chapterwise for Class 10 Science, Mastering Numericals and Objectives of Physics for Class X, On the same side of the lens as the object, Between infinity and optical center O of the lens, Light is a form of energy due to which we are able to see the objects which emits light for example objects like sun,