NEET Class neet Answered
if focal length of objective lens is 40 cm , then lens-to-image distance vo of image fromed from an object that is at a distance 200 cm from objective lens is calculated from lens equation
In above equation v = vo , u = -200 cm and f = 40 vm
Image formed by objective lens is object of eyepiece.
Let ue is the lens-to-object distance of eyepiece. We want lens-to-image distance of eyepiece as D = 25 cm ( least distance of distinct vision ).
Hence we get from lens equation as
where fe is focal length of eye piece lens .
Hence ue = -3.45 cm
Distance d between objective lens and eyepiece is
d = | vo | + | ue | = ( 50 + 3.45 ) cm = 53.45 cm
( we can consider the round-off distance as 54 cm )