aperture

Examples of aperture in the following topics:

• The Camera

  • The two major features of a lens are focal length and aperture.
  • The focal length determines the magnification of the image, and the aperture controls the light intensity.
  • The shutter is what opens and closes to allow light through the aperture.
  • For a larger aperture, the f-number is generally small for a quick shutter speed.
  • For a smaller aperture, the f-number is larger, allowing for a slower shutter speed.

• The Rayleigh Criterion

  • (a) shows a light passing through a small circular aperture.
  • This effect can be seen with light passing through small apertures or larger apertures.
  • θ - angle the objects are separated by, in radian λ - wavelength of light D - aperture diameter. shows this concept visually.
  • (a) This is a graph of intensity of the diffraction pattern for a circular aperture.
  • (a) Monochromatic light passed through a small circular aperture produces this diffraction pattern.

• Limits of Resolution and Circular Aperatures

  • For telescopes with circular apertures, the size of the smallest feature in an image that is diffraction limited is the size of the Airy disc, as shown in .
  • As one decreases the size of the aperture in a lens, diffraction increases and the ring features from diffraction become more prominent.
  • The denominator $nsin \theta$ is called the numerical aperture and can reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.

• Resolution of the Human Eye

  • The pupil of the human eye is its aperture.
  • The iris is the diaphragm that serves as the aperture stop.
  • Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter.

• Photography: Recording an Image

  • Lens aperture - The size of the opening behind the lens.
  • A larger aperture will allow more light to pass through the lens than a smaller one.
  • The total amount of light reaching the film plane is known as the exposure, and changes according to the shutter speed, the aperture of the lens, and the effective focal length of the lens.

• Diffraction

  • Intensity pattern formed on a screen by diffraction from a square aperture.

• Pelvimetry

• The Heisenberg Uncertainty Principle

  • If a large aperture is used for the microscope, the electron's location can be well resolved (see Rayleigh criterion); but by the principle of conservation of momentum, the transverse momentum of the incoming photon and hence the new momentum of the electron resolves poorly.
  • If a small aperture is used, the accuracy of both resolutions is the other way around.

• The Human Eye

  • The human eye is had an aperture, just like a camera.
  • The pupil serves this function, and the iris is the aperture stop.

• Inguinal Hernia

  • It is not considered to provide a cure, and if the pads are hard and intrude into the hernia aperture they may cause scarring and enlargement of the aperture.