Move the mirror forward and backwards to obtain a sharp image on the wall. Your email address will not be published. It contains the … The image of the building is obtained on a wall which is painted white. sun or a distant building can … u – v graph is obtained by considering u on the x’- axis and v on y’ – axis. The rough focal length of the given concave mirror = ……. Example 4: An object is placed at a distance of 15 cm from a concave mirror of focal length 10 cm. Hold the concave mirror in sun. The distance between the selected distinct object should be more than 50 ft. Form the sharpest possible image of the Sun on some surface. and semiconductor devices, Measurement of resistance and potential difference, Potential Energy and Conservation of Energy. Q3. For point A, the values of u and v will be the same. CBSE Class 10 Science Lab Manual – Focal Length of Concave Mirror and Convex Lens EXPERIMENT 4(a) Aim To determine the focal length of concave mirror by obtaining the image of a distant object. Q2. Online physics calculator that calculates the concave mirror equation from the given values of object distance (do), the image distance (di), and the focal length (f). Observed distance between the mirror and image needle when knitting needle is placed in between the, z = …….. Index correction for the object distance, u = x – y = ±……. Form the sharpest possible image of the Sun on some surface. To make the tip of the image needle and tip of the image inline, adjust the height of the image needle by closing the left eye and opening the right eye. It is represented by the symbol f. For mirrors of small aperture, f=R/2. The image distance \(d_i\) is positive for real images and negative for virtual images. Following are the materials required for this experiment: We use mirror formula for the determination of focal length. Place the concave mirror in the mirror holder. To determine the focal length of a concave mirror, by obtaining image of a distant object. Move the mirror forward and backwards to obtain a sharp image on the wall. On either axis draw a line OA making 45° and meeting at a point A. To set the mirror 1. Using the observation table, plot different points for different values of u and v. The graph obtained will be a rectangular parabola. Solution: We have u = –15 cm and f = –10 cm Focal length. By obtaining the Real image of a distant object at its focus, the focal length of the concave mirror can be estimated as shown in the diagram. 3. The placement of the fixed upright should be near zero ends of the optical bench while … The same can also be proved by using the mirror formula: (1/f = … Let O be the thin optical needle which is mounted on the second upright. What is the optical centre of a lens? Repeat the process two or three times. The focal length \(f\) is positive for concave mirrors and negative for convex mirrors. You will see a very bright spot and the surface where the image is formed will get hot. To get observations 4, 5, and 6, move the object needle away from the mirror by 1 cm. Let the distance between the plane mirror and the concave mirror= l and the object is placed at x distance from the plane mirror. 4. Your email address will not be published. Thus, the focal length of a concave mirror can be estimated by obtaining a 'Real image' of a distant object at its focus, as shown in the figure. At the base of the mirror upright, note the position of the index mark. It's similar to the way we fi d the focal length of a convex lens. The concave mirror placed on the mirror stand and the distant object should be facing each other. Materials Required. The coordinates at A is (2f, 2f) as u and v are same for a concave mirror when the object is placed at the centre of curvature. Attach the mirror to the holder at the fixed upright such that the mirror faces towards the other end of the bench and surface where it is perpendicular to the length. Principal section. The placement of the fixed upright should be near zero ends of the optical bench while the other two uprights must be near the other ends. Hence, u = v = R = 2f. The eye should be at least 30 cm away from the needle to locate the position of the image. Ans: Principal axis of a lens is the straight line passing through the centre of curvature of the lens. The focal length of the convex mirror is positive, whereas that of the concave mirror is negative. Drag the screen by clicking on point A of the screen till you get a sharp image of the objec t. Measure the distance between the concave mirror and the screen with given metre scale. https://physicsmax.com/to-measure-the-focal-length-of-a-concave-mirror-6838 A concave mirror, like a plane mirror, obeys the laws of reflection of light. Both the axes are cut by a straight line at 45° making equal intercepts. The focal length of the given concave mirror is determined from the following: Ans: Lens formula is defined as the equation which explains the relation between object distance (u), image distance (v), and focal length of the lens (f).