CBSE Class 10 Science 2019 · Paper 31/1/1/C · Question 27(b)

1. Fix the convex lens in a lens holder and place it on a table near an open window, facing a distant object such as a tree or a building. 2. Place a white screen in a stand on the other side of the lens, with the object, the lens and the screen in a straight line. 3. Move the screen (or the lens) back and forth until a sharp, inverted and diminished image of the distant object is formed on the screen. 4. Measure the distance between the lens and the screen with a metre scale; this distance is the focal length of the lens. (Repeat with other distant objects and take the mean.)