An angular magnification (magnifying power) of 30X is desired using an objective of focal length 1.25 cm and an eyepiece of focal length 5 cm. How will you set up the compound microscope?
Focal length of the objective lens, fo=1.25cm Focal length of the eyepiece, fe=5cm Least distance of distinct vision, d=25cm Angular magnification of the compound microscope = 30X Total magnifying power of the compound microscope, m=30 The angular magnification of the eyepiece is given by the relation- me=(1+d/fe)=6 The angular magnification of the objective lens (mo) is calculated as- mome=m⇒mo=5 Now, mo=−vo/uo⇒vo=−5uo Using lens formula, vo1−uo1=fo1 Using above two equations, uo= −1.5cm and vo=7.5cm So, The object should be placed 1.5 cm away from the objective lens to obtain the desired magnification. Now, Image distance for the eyepiece is ve=−d=−25cm Using lens formula, ve1−ue1=fe1 ue=−4.17cm Separation between the objective lens and the eyepiece, ∣ue∣+∣vo∣=11.67cm Therefore, the separation between the objective lens and the eyepiece should be 11.67cm.
