Optics 3 Question 34

34. The focal length of a thin biconvex lens is 20cm. When an object is moved from a distance of 25cm in front of it to 50cm, the magnification of its image changes from m25 to m50. The ratio m25m50 is

(2010)

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Answer:

Correct Answer: 34. 6

Solution:

  1. 1v1u=1f or uv1=uf or uv=(u+ff)

m=vu=(fu+f)m25m50=2025+202050+20=6

Answer is 6 .



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