Question

A student was asked by his teacher to find the image distance for various object distance in case of a given convex lens. He performed the experiment with all precautions and noted down his observations in the following table:
S.No
1
2
3
4
5
6

Object distance (cm)
60
48
36
24
18
16

Image distance (cm)
15
16
21
24
36
48

After checking the observations table the teacher pointed out that there is a mistake in recording the image distance in one of the observations. Find the serial number of the observations having faulty image distance.
(A) 2
(B) 3
(C) 5
(D) 6

Answer 1

the correct answer is B

3.    36   21    is wrong observation.

In all other cases f = 12 cm. For this alone f = 13. 2 cm.