Final answer:
Numerical Aperture (NA) is a measure of the light-gathering qualities of a lens and is a constant value for each lens. It is calculated using the formula NA = n sin α, where n is the refractive index of the medium and α is half the acceptance angle for light rays. NA is important in microscopy as it relates to the lens's ability to gather light and resolve finer details.
Step-by-step explanation:
The measure of the light-gathering qualities of a lens and a constant value for each lens is called Numerical Aperture (NA). NA is calculated using the formula NA = n sin α, where n is the refractive index of the medium between the lens and the object, and α is half the acceptance angle for light rays. NA is important in microscopy as it determines the lens's ability to gather light and resolve finer details.