. A compound microscope consists of an objective lens of focal length

2.0cm and an eyepiece of focal length 6.25cm separated by a distance of 15cm .

How far from the objective should an object be placed in order to obtain the final image at:

(a) the least distance of distinct vision (25cm) , and

(b) at infinity? What is the magnifying power of the microscope in each case?

Explanation:

1/v_e-1/u_e=1/f_e

⇒1/-25-1/u_e=1/6.25

⇒u_e=-5cm

1/v_o-1/u_o=1/f_o

⇒1/10-1/u_o=1/2

⇒u_o=-2.5cm

Image distance for the eyepiece, ve=-∞

Object distance for the eyepiece, is u_e

Applying lens formula for eyepiece lens,

1/v_e-1/u_e=1/f_e

⇒1/-∞-1/u_e=1/6.25

⇒u_e=-6.25cm

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