Question

Analyze the following observation table showing variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations : S. No.
Object-Distance
u (cm)
Image-Distance
v (cm)
1
–100
+25
2
–60
+30
3
–40
+40
4
–30
+60
5
–25
+100
6
–15
+120
(a) What is the focal length of the convex lens? Give reason to justify your answer.
(b) Write the serial number of the observation which is not correct. On what basis have you arrived at this conclusion?
(c) Select an appropriate scale and draw a ray diagram for the observation at S.No. 2. Also find the approximate value of magnification.

Answer 1

1)that focal leave of a convex lence is a point c to p