ABSTRACT
In this chapter, geometrical (ray) optics is used to understand the key attributes of lenses, which are devices commonly used to redirect visible electromagnetic radiation and create an image. The chapter begins with a discussion of key types of lenses, notably converging and diverging lenses, and their important attributes, including lens focal length and power, and lens aberrations. This is followed by a discussion of two methods of determining the location, type (i.e., real or virtual), and magnification of the image created by a simple lens: ray tracing and lens equations. The chapter concludes with a discussion of the role that lenses play in vision and in a research-grade microscope. The latter is a device that generates images of exceptional quality and that is used, with appropriate adaptations, in essentially all forms of light microscopy. The reader is introduced to the lenses and diaphragms that make up the optical train in a research-grade microscope, the concept of conjugate planes, Köhler illumination, and light (illumination) sources.
