Chapter 27, Problem 93GP

Landing on an Aircraft Carrier The Fresnel Lens Optical Landing System (FLOLS) used to ensure safe landings on aircraft carriers consists of a series of Fresnel lenses of different colors. Each lens focuses light in a different, specific direction, and hence which light a pilot sees on approach determines whether the plane is above, below, or on the proper landing path. The basic idea behind a Fresnel lens, which has the same optical properties as an ordinary lens is shown in Figure 27-30. Suppose an object is 17.1 cm behind a Fresnel lens, and that the corresponding image is a distance d₁ = d in front of the lens. If the object is moved to a distance of 12.0 cm behind the lens, the image distance doubles to d = 2d. In the FLOLS, it is desired to have the image of the lightbulb at infinity. What object distance will give this result for this particular lens?

A lens causes light to refract at its surface; therefore, the interior glass can be removed without changing its optical properties. This produces a Fresnel lens, which is much lighter than the original lens. (Problem 93)