contestada

A converging lens has a focal length of 20 cm. An object 1 cm tall is placed 10 cm from the center of the lens. What is the height of the image? (note: solve for the image distance first)

Respuesta :

Answer: 2 cm

Explanation:

Given , for a converging lens

Focal length : [tex]f=20\ cm[/tex]

Height of object : [tex]h=1\ cm[/tex]

Object distabce from lens : [tex]u=-10\ cm[/tex]

Using lens formula: [tex]\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}[/tex], we get

[tex]\dfrac{1}{20}=\dfrac{1}{v}+\dfrac{1}{10}[/tex], where v = image distance from the lens.

On solving aboive equation , we get

[tex]\dfrac{1}{v}=\dfrac{1}{20}-\dfrac{1}{10}=\dfrac{1-2}{20}=\dfrac{-1}{20}\Rightarrow\ v=-20\ cm[/tex]

Formula of Magnification : [tex]m=\dfrac{v}{u}=\dfrac{h'}{h}[/tex] , where h' is the height of image.

Put value of u, v and h in it , we get

[tex]\dfrac{-20}{-10}=\dfrac{h'}{1}\\\\\Rightarrow\ h'=2\ cm[/tex]

Hence, the height of the image is 2 cm.

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