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# Form 4 Physics online lessons on thin lenses

Lesson on Linear magnification.

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Linear magnification.
The linear magnification produced by a lens defined as the ratio of the height of the image to the height of the object, denoted by letter ‘m’, therefore;
m = height of the image /height of the object. Magnification is also given by = distance of the image from the lens/ dist. of object from lens.
m =v/u
Example
An object 0.05 m high is placed 0.15 m in front of a convex lens of focal length 0.1 m. Find by construction, the position, nature and size of
the image. What is the magnification?
Solution
Let 1 cm represent 5 cm.
hence 0.05 m = 5 cm = 1 cm –object height
0.15 m = 15 cm = 3 cm
0.1 m = 10 cm = 2 cm – focal length.

a) Image formed is beyond 2 F
- Inverted
- Real
- Magnified
b) magnification=v/u=frac{30cm}{15cm}=2

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