Explanation:
We have,
Height of object is 5 cm
Object distance from a convex lens is 18 cm
Focal length of convex lens is 10 cm
i.e. h = 5 cm
u = -18 cm
f = +10 cm
Let v is distance of the image from the lens. Using lens formula :
[tex]\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}\\\\\dfrac{1}{v}=\dfrac{1}{f}+\dfrac{1}{u}\\\\\dfrac{1}{v}=\dfrac{1}{10}+\dfrac{1}{(-18)}\\\\v=22.5\ cm[/tex]
The magnification of lens is :
[tex]m=\dfrac{v}{u}=\dfrac{h'}{h}[/tex], h' is height of the image
[tex]\dfrac{v}{u}=\dfrac{h'}{h}\\\\h'=\dfrac{vh}{u}\\\\h'=\dfrac{22.5\times 4}{(-18)}\\\\h'=-5\ cm[/tex]
h' = -5.00 cm (in three significant figures)
