400×

400× is a notation that uses the multiplication sign to express a factor of 400. The symbol × indicates “times” and is widely used to show a scale or multiplier in various disciplines.

In mathematics, 400× a means 400 multiplied by a, representing a proportional relationship or an operation on a quantity. The concept is straightforward: 400 is the scalar by which another value is scaled.

In imaging and microscopy, 400× refers to magnification—the apparent enlargement of an object relative to its actual size. Magnification is achieved by combining lenses in optical systems; a common arrangement on light microscopes is a 40× objective lens paired with a 10× eyepiece to yield about 400× magnification. Higher magnifications are possible with different lens combinations or with digital enhancements, though resolution is limited by the optical system and wavelength of light.

Beyond mathematics and imaging, 400× can indicate a 400-fold increase or scale in other contexts, such as data throughput, growth, or experimental factors. The precise meaning depends on the accompanying units, quantities, or descriptive terms.

Because the symbol × is used for multiplication and as a cross, the meaning of 400× is context-dependent and may be ambiguous without clarification. See also Multiplication and Magnification for related concepts.