CBSE Class 10 Science 2019 · Paper 31/5/1 · Question 24

A teacher gives a convex lens and a concave mirror of focal length of 20 cm each to his student and asks him to find their focal lengths by obtaining the image of a distant object. The student uses a distant tree as the object and obtains its sharp image, one by one, on a screen. The distances $d_1$ and $d_2$ between the lens/mirror and the screen in the two cases and the nature of their respective sharp images are likely to be Give reason for your answer.