Magnification and Calibration
Key Terms
Magnification – how many times larger the image is
than the actual size of the specimen
Resolution – the ability to distinguish between two
close together objects
Light Microscopes
Light (or optical) microscopes use lenses to project a
magnified image of an object onto the eye.
Magnification is a measure of how many times bigger
the image is than the object:
Magnification = size of image / actual size of the object
Light microscopes are limited to a magnification of
1500× by their resolving power (resolution). This is a
measure of their ability to distinguish between two
separate points. A light microscope cannot resolve two
points that are closer than half a wavelength of visible
light (250 nm).
Example:
Measured length of phage = 29mm
Magnification = 29 ÷ 0.0002 =
145000
Magnification = 1.45 x 105
Key Terms
Magnification – how many times larger the image is
than the actual size of the specimen
Resolution – the ability to distinguish between two
close together objects
Light Microscopes
Light (or optical) microscopes use lenses to project a
magnified image of an object onto the eye.
Magnification is a measure of how many times bigger
the image is than the object:
Magnification = size of image / actual size of the object
Light microscopes are limited to a magnification of
1500× by their resolving power (resolution). This is a
measure of their ability to distinguish between two
separate points. A light microscope cannot resolve two
points that are closer than half a wavelength of visible
light (250 nm).
Example:
Measured length of phage = 29mm
Magnification = 29 ÷ 0.0002 =
145000
Magnification = 1.45 x 105
