PHYS 117 Chapter Notes - Chapter 25: F-Number, Far Point, Far-Sightedness
Document Summary
The intensity of the light reaching the film is proportional to the area of the lens. The ratio of focal length to diameter is called the f-number (or focal ratio) of a lens. Low f-number = faster lens (wide open aperture and the maximum possible lens area) Large depth of field means that objects at a wide range of distances from the lens form reasonably sharp images on the film (meaning camera doesn"t have to be focused) Most of the refraction occurs at the outer surface of the eye, where the cornea is covered in a film of tears. Accommodation: the eye focuses on an object by varying the shape of the pliable crystalline lens. Near point: the closest distance for which the lens can accommodate to focus light on the retina. Far point: the farthest distance for which the lens of the relaxed eye can focus light on the retina.
