Question

R The Expert TA J Huma X (6%) Problem 5: Suppose a book " held 6.7cm fiom a 12.5cm fral length lens for 50% Part (a) Find the magnification of the image ofthe book. upleted 14.43 mpleted mpleted tial mpleted mpleted mpleted cotanan aco atan) acota i) cosh tanhcotanb . Degrees O Radians I gie up mpleted Notice hat you do not ksow the image distance for the bock You w mpletedhave t rtial to elninabe the image distance bry isng the magmifionon and this lena equahon ▲50% Part (b) Find themagnification ofd e lens when the book theld ucm he the mar ter mpleted 8 0

Answer 1

Object distance from lens

Focal length of lens

a)

Thin lens formula: $\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

$\frac{1}{v}=\frac{1}{f}-\frac{1}{u}$

Image distance from lens is $v=\frac{uf}{u-f}=\frac{6.7*12.5}{6.7-12.5}=-14.44\,cm$

Magnification of image of book is $m=-\frac{v}{u}=-\frac{-14.44}{6.7}=2.16$

Part b)

Now , object distance is

Thin lens formula: $\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

$\frac{1}{v}=\frac{1}{f}-\frac{1}{u}$

Image distance from lens is $v=\frac{uf}{u-f}=\frac{8.1*12.5}{8.1-12.5}=-23.01\,cm$

Magnification of image of book is $m=-\frac{v}{u}=-\frac{-23.01}{8.1}=2.84$

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