Wave length 500 nm. Refractive index 1 angular aperture sin 90
Answers
Wave length 500 nm. Refractive index 1 angular aperture sin 90
Answer:
The numerical aperture of a microscope objective is a measure of its ability to gather light and resolve fine specimen detail at a fixed object distance. Image-forming light waves pass through the specimen and enter the objective in an inverted cone as illustrated in Figure 1. A longitudinal slice of this cone of light shows the angular aperture, a value that is determined by the focal length of the objective.
The angle µ is one-half the angular aperture (A) and is related to the numerical aperture through the following equation:
Numerical Aperture (NA) = n(sin µ)
where n is the refractive index of the imaging medium between the front lens of the objective and the specimen cover glass, a value that ranges from 1.00 for air to 1.51 for specialized immersion oils. Many authors substitute the variable α for µ in the numerical aperture equation. From this equation it is obvious that when the imaging medium is air (with a refractive index, n = 1.0), then the numerical aperture is dependent only upon the angle µ whose maximum value is 90°. The sin of the angle µ, therefore, has a maximum value of 1.0 (sin(90°) = 1), which is the theoretical maximum numerical aperture of a lens operating with air as the imaging medium (using "dry" microscope objectives).