Linear Magnification
- The magnification of a lens is equal to the ratios of the image height and the object height
- This equation can be rearranged with the help of a formula triangle:
Magnification Formula Triangle
Magnification, image height and object height formula triangle
- The magnification depends on:
- The distance of an object from the lens
- The power of the lens
- The units for height are unimportant, provided that both the object and image are measured in the same units
- For example, both in cm, or both in mm
- Therefore, magnification does not have units as it is a ratio
- If the magnification is:
- > 1, then the image is magnified
- = 1, then the object and image are the same size
- < 1, then the image isĀ diminished
Worked example
A person sees an image from a magnifying glass. Calculate the magnification of this image. Clearly show your working on the diagram.
Answer:
Step 1: Measure the height of the object and image from the scale
- The object is 10 cm
- The image is 20 cm
Step 2: Substitute values into the magnification equation