Chapter 28, Problem 87GP

BIO Entoptic Halos Images produced by structures within the eye (like lens fibers or cell fragments) are referred to as entoptic images These images can sometimes take the form of “halos” around a bright light seen against a dark background. The halo in such a case is actually the bright outer rings of a circular diffraction pattern like Figure 28-29 with the central bright spot not visible because it overlaps the direct image of the light. Find the diameter of the eye structure that causes a circular diffraction pattern with the first dark ring at an angle of 2.7° when viewed with monochromatic light of wavelength 605 nm. (Typical eye structures of this type have diameters on the order of 10μm. Also, the index of refraction of the vitreous humor is 1.36.)