Optics Question 788

Question: When an object is placed at a distance of 25 cm from a mirror, the magnification is m1 . The object is moved 15cm further away with respect to the earlier position, and the magnification becomes If m1/m2=4, the focal length of the mirror is:

Options:

A) 10 cm

B) 30 cm

C) 15 cm

D) 20 cm

Show Answer

Answer:

Correct Answer: D

Solution:

[d] m=vu(fuf)

Now m1=(f25f) –(i)

and m2=(f40f) –(ii)

m1m2=40f25f or 4=40f25f or f=20cm.



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