Numerical aperture

Numerical aperture (NA) is a measure of how well a microscope lens can gather light and resolve fine details in a sample. It indicates the lens's light-gathering ability and its capacity to distinguish between closely spaced objects. A higher NA means the lens can collect more light and produce sharper, clearer images, especially important at high magnifications. NA depends on the lens design and the refractive index of the medium between the lens and the specimen. In summary, NA is a key factor determining the clarity and detail a microscope can achieve.