numerical aperture


nu·​mer·​i·​cal aperture n(y)u̇-ˈmer-i-kəl- How to pronounce numerical aperture (audio)
: a number that indicates the resolving power of a microscope objective and is equal to the product of the index of refraction of the medium (as immersion oil) in front of the objective and the sine of half the angle formed by two rays emanating from the object upon which the microscope is focused and entering the objective at either end of a diameter of the objective

Dictionary Entries Near numerical aperture

Cite this Entry

“Numerical aperture.” Medical Dictionary, Merriam-Webster, Accessed 28 Mar. 2023.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

A Good Old-Fashioned Quiz

True or False

Test your knowledge - and maybe learn something along the way.

Solve today's spelling word game by finding as many words as you can with using just 7 letters. Longer words score more points.

Can you make 12 words with 7 letters?