Three thin lenses are combined by placing them in contact with each other to get more magnification in an optical instrement. Each lens has a focal length of 3 cm. If the least distance of distinct vision is taken as 25 cm, the total magnification of the lens combination in normal adjustment is

Options

A. 9
B. 26
C. 300
D. 3

Explanation

Combined focal length `((1)/(F))=(1)/(F_(1))+(1)/(F_(2))+(1)/(F_(3))`
`rArr(1)/(F)=(1)/(3)+(1)/(3)+(1)/(3)` `rArr " " F = 1 cm`
Magnification of the lens combination in normal adjustment is
`M=1+(D)/(F)=1+(25)/(1)=26`