Phaos Optic Science Educational Series

March 15, 2021
12:00 PM (GMT)

10 Minutes



In microscopy context, it refers to the amount or degree of visual enlargement of an observed object.

Magnification is measured by multiples, such as 2x, 4x and 10x, indicating that the object is enlarged to twice as big, four times as big or 10 times as big, respectively.


Simple magnifier lenses are bi-convex. This means that it is thicker at the center as compared to the periphery. When light pass through the biconvex lens, the parallel rays of incident light will converge at the focal point, as shown in the figure below.

  • Focal Length (or focal distance): Distance between the center of a converging thin lens and the point at which parallel rays of incident light converge OR distance between the center of a diverging lens and the point from which parallel rays of light appear to diverge
  • Focal Point: The point at which it intersects the focal plane.
  • Optical Element-Image Distance: The distance from the lens to the image

If a biconvex lens is near an object inside its focal point, a virtual upright image can be seen. The lenses of the microscope’s eyepiece create a virtual image because your eye is within the focal point.  The eyepiece will only enlarge the image of the specimen.

Cr/ SchoolPhysics

On the contrary, if the objective lens focuses on the specimen outside the focal point creating a real image.  This image from the objective will increases the detail or resolving power of that specimen, leading to a new terminology called Resolution. This allows users to look into a microworld. Hence, the higher the objective lens the better the resolution. (We will talk about it in the next post)

Do note that eyepiece do not contribute anything to the image where it simply spreads out the details.  This is why it is also referred as empty magnification and has less than 20 times magnification.

Magnification Limits

Typically, a standard light-based microscope has a maximum magnification up to 1,500x. Any magnification beyond this will cause the image to be excessively fuzzy as the wavelengths of light will limits the clarity of image.