Question

The figure shows a combination of two lenses. (Figure 1)

Part A

Find the position of the final image of the 1.0-cm-tall object.

Express your answer using two significant figures.

Part B

Find the size of the final image of the 1.0-cm-tall object.

Express your answer using two significant figures.

Part C

Find the orientation of the final image of the 1.0-cm-tall object.

Answer 1

A) apply for converging lens \(1 / \mathrm{f}=1 / \mathrm{u} 1+1 / \mathrm{v} 1\)

\(1 / v 1=1 / 5-1 / 4\)

\(\mathrm{v} 1=-20 \mathrm{~cm}\) (image distance for the first lense)

\(f 2=-8 \mathrm{~cm}\)

\(\mathrm{u} 2=-20-12=-32 \mathrm{~cm}\) (object distance for the second lense)

\(1 / \mathrm{u} 2+1 / \mathrm{v} 2=1 / \mathrm{f} 2\)

\(1 / v 2=1 / f 2-1 / u 2\)

\(1 / v 2=-1 / 8-1 / 32\)

\(v 2=-6.4 \mathrm{~cm}\)

from object \(12-6.4+4 =9.6 \mathrm{~cm}\)

B) magnification, \(\mathrm{m}=(-\mathrm{v} 1 / \mathrm{u} 1)^{*}(-\mathrm{v} 2 / \mathrm{u} 2)\)

\(=(20 / 4)^{*}(6.4 / 32)\)

\(=1\)

imahe height \(=\mathrm{m}^{*}\) object height

\(=1^{*} 1\)

\(=1 \mathrm{~cm}\)

C) erect