Question

while finding out the focal length of convex lens, Ash ok kept it on the optical bench 10.5cm .He adjusts to the stand carrying the screen to obtain sharp image of distant tree on it and finally got it when this stand was at 20.8cm on the optical bench. What is the focal length:
A) 10.3 cm
B) 10.5 cm
C) 20.8 cm
D) 5.1 cm

Answer 1

C). 20.8 cm
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