Analysis the following observation table showing variation of image distance (v) with object distance (u) in case of a convex - Science - Light - Reflection and Refraction

Question

Analysis 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 calculation:

Anshu Agrawal · Accepted Answer

Solution:
a)focal length will be half of radius of curvature as we already known and object placed on centre of curvature forms image at the same pointSo in this table,this point is 40cm as in this case only object and image distance is equalso focal length=-20cmb) serial number 6 is incorrect as the object is placed between focus and pole and still the image is formed real which is not possible 
image distance must be negative in this case
c)
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Analysis 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 calculation: