Question

Analyse 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

The question may not be complete one and missing table . please  find the table in the attachment

Prmkulk1978  has already given  good answer already at

https://brainly.in/question/2435981#readmore

1.From the observation 3, we can say that Radius of curvature is 40cm so foal length of the convex lens is 20cm.[f=R/2]

2. Observation 6 is incorrect , as the object is in between P and F, the image formed will be virtual image on the same side of object, image distance should be negative.

3.Ray diagram for observation 3: Please refer attachment : object beyond C

4. magnification=m=v/um=30/-60=-1/2= -0.5so the image is real, inverted and diminished.