Answer to Question #207988 in Electricity and Magnetism for Kasie

Question

An amoeba is 0.305cm away from the 0.300cm focal length objective lens

of a microscope. (Use the thin lens formula and the magnification

formula)

A. Where is the image formed by the objective lens?

B. What is the image magnification?

C. An eyepiece with a 2.00cm focal length is placed 20.0cm from the

objective. Where is the final image?

Answer 1

Gives

Object distance $d_o=0.305cm$

Focal length

$f_o=0.300$

We know that

Part(a)

$\frac{1}{f}=\frac{1}{d_i}+\frac{1}{d_o}$

$\frac{1}{d_i}=\frac{1}{f}-\frac{1}{d_o}$

$\frac{1}{d_i}=\frac{1}{0.300}-\frac{1}{0.305}$

$d_i=18.3cm$

Part(b)

Magnification (m) $=-\frac{d_i}{d_o}$

$m=-\frac{18.3}{0.305}=-60$

Part(c)

$f_o=2.00cm$

$d'_o=20-18.3=1.70cm$

We know that

$\frac{1}{d'_i}=\frac{1}{f_o}-\frac{1}{d'_0}$

$\frac{1}{d'_i}=\frac{1}{2.00}-\frac{1}{1.70}=-\frac{3}{34}$

$d'_i=-11.33cm$