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.1 +182 −60 +203 −30 +30No.Object distance u (cm)−90−60−30−20−18−10Image distance v (cm)+18+20+30+60+90+100(a) What is the focal length of the convex lens? Give reason in support of your answer.
(b) Write the serial number of that observation which is not correct. How did you arrive at this conclusion?
(c) Take an appropriate scale to draw ray diagram for the observation at S. No. 4 and find the approximate value of magnication.

Answer 1

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Please find the question as an attachment. Hope so the solution helps you.

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.