The focal length is half the radius of curvature. Focal length. Materials Required A concave mirror, a mirror holder, a small screen fixed on a stand, a measuring scale and a distant object (a tree visible clearly through an open window). Example 4: An object is placed at a distance of 15 cm from a concave mirror of focal length 10 cm. Find the position of the image. Solution: We have u = ā¦ The distance between the needle and the lens gives the focal length of the lens. Solution: The radius of curvature of the mirror = 30 cm Thus, the focal length of the mirror =\(\frac { 30 cm }{ 2 } \) = 15 cm. A convex mirror is sometimes referred to as a diverging mirror due to the fact that incident light originating from the same point and will reflect off the mirror surface and diverge. is the distance between the pole P and the principal focus F of a curved mirror. The principal focus is in front of the concave mirror and is behind the convex mirror. 4s s -d f 2 2 = , where = d d -d 1 2 Finally, determine the mean focal length. In that case, the image is virtual, upright, and enlarged. EXPERIMENT 4(a) Aim To determine the focal length of concave mirror by obtaining the image of a distant object. Since the focal point is located behind the convex mirror, such a mirror is said to have a negative focal length value. The parallel beam of light is reflected back along the same path and forms the image Pā of the tip P at the focus of the lens. Radius of curvature = 2 ā Focal length (f) R= 2f= R/2 = 32/2 = 16 Hence, the focal length of the given convex mirror is 16 cm. In diagram, PF is the focal length of the mirror. It is represented by the symbol f. For mirrors of small aperture, f=R/2. Principal section. Find the distance between then mirrors in terms of f 1 and f 2. Rules for constructing ray diagrams. Focal length: The focal length (denoted by FP in the fig.) Focal length = Radius of curvature/2 . Calculate the focal length of the convex lens by using the formula given. Example: Look at the path of the ray R in the given picture, f 1 is the focal length of the convex mirror and f 2 is the focal length of the concave mirror. Lies in front of the mirror and focal length is positive: Image: Virtual, upright, and diminished: Real and inverted, except when the object is placed between the pole and the focus. The distance between the pole and the principal focus of the mirror, is called the focal length of the mirror. In this position rays of light starting from the tip of the pingo parallel to the principal axis and strike the reflecting surface of the mirror M normally. CBSE Class 10 Science Lab Manual ā Focal Length of Concave Mirror and Convex Lens.