# Problem: An object is located 30.0 cm from a certain lens. The lens forms a real image that is twice as high as the object. What is the focal length of this lens? a. 90 0 cm b. 10.0 cm c. 5.00 cm d. 20.0 cm

###### FREE Expert Solution

Lens equation:

$\overline{)\frac{\mathbf{1}}{\mathbf{f}}{\mathbf{=}}\frac{\mathbf{1}}{{\mathbf{s}}_{\mathbf{o}}}{\mathbf{+}}\frac{\mathbf{1}}{{\mathbf{s}}_{\mathbf{i}}}}$

Magnification:

$\overline{){\mathbf{m}}{\mathbf{=}}\frac{{\mathbf{h}}_{\mathbf{i}}}{{\mathbf{h}}_{\mathbf{o}}}{\mathbf{=}}{\mathbf{-}}\frac{{\mathbf{s}}_{\mathbf{i}}}{{\mathbf{s}}_{\mathbf{o}}}}$

m = hi/ho = 2

For a real image, distance is negative.

###### Problem Details

An object is located 30.0 cm from a certain lens. The lens forms a real image that is twice as high as the object. What is the focal length of this lens?

a. 90 0 cm

b. 10.0 cm

c. 5.00 cm

d. 20.0 cm

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Thin Lens And Lens Maker Equations concept. You can view video lessons to learn Thin Lens And Lens Maker Equations. Or if you need more Thin Lens And Lens Maker Equations practice, you can also practice Thin Lens And Lens Maker Equations practice problems.