When the object is at distances a_1 and a_2 the images formed by the same lens are real and virtual respectively and of the same size. Then focal length of the lens is:

When the object is at distances a_1 and a_2 the images formed by the s

1.	When the object is at distances a_1 and a_2 the images formed by the same lens are real and virtual respectively and of the same size. Then focal length of the lens is:
Answer» SOLUTION :Magnification `m=F/(f+u)` [use SIG convention in this formula] According to the question `m_1=-m_2 implies (f/(f-mu_1))=-(f/(f-mu_2))implies f=(mu_1+mu_2)/2`