Problem 22.72 A microscope has an objective lens of focal length+0.50-cm and an

Question

Problem 22.72

A microscope has an objective lens of focal length+0.50-cm and an eyepiece of focal length+2.6-cm. An object is placed 0.60 cm in front of the objective lens. The final virtual image is100 cm from the eyepiece at the position of minimum eyestrain.

Part A

Determine the separation of the lenses. Assume that the near point distance is 25 cm.

Express your answer to two significant figures and include the appropriate units.

Part B

Determine the total angular magnification.

Express your answer using two significant figures.

Problem 22.72

A microscope has an objective lens of focal length+0.50-cm and an eyepiece of focal length+2.6-cm. An object is placed 0.60 cm in front of the objective lens. The final virtual image is100 cm from the eyepiece at the position of minimum eyestrain.

Part A

Determine the separation of the lenses. Assume that the near point distance is 25 cm.

Express your answer to two significant figures and include the appropriate units.

Part B

Determine the total angular magnification.

Express your answer using two significant figures.

Explanation / Answer

step 1:
for objective lens:

object distance=u=-0.6 cm
focal length=f=0.5 cm
let the image distance be v.
then using lens equation:
(1/v)-(1/u)=1/f

==> v=3 cm

so a real and inverted image will be formed at a distance of 3 cm from the objective lens.

magnification achieved=image distance/object distance=3/-0.6=-5

step 2:

for the eye piece:
let the separation of the lenses be d.

then assuming d> 3 cm,

object distance for eye piece=u=-(d-3) cm
focal length=f=2.6 cm
image distance=v=-100 cm

using lens equation, we get d=5.53 cm

part B:

total angular magnification=-5*100/(d-3)=-197.62

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