Fig. 36-1 A typical single lens reflex camera. The lens has many elements cemented together to form a single compound lens.

Fig. 36-2 The larger image size with a larger value of f corresponds to a smaller angle of view.

Fig. 36-3 In a camera lens, larger f-numbers mean smaller aperture diameters. f-number = f / D where D = diameter of aperture

Fig. 36-4 Principle of zoom lens: use two elements with variable spacing. The effective focal length depends on the distance between the two optical elements.

Fig. 36-6 Overhead projector. The inexpensive plastic Fresnel lens is like an ordinary thick lens with the internal material removed.

Fig. 36-7 The eye. The muscle contracts to change the focal length of the lens to image close objects.

Fig. 36-8 Refractive errors for a myopic (nearsighted) eye and a hyperopic (farsighted) eye viewing a very distant object. The dashed blue curve indicates the correct position of the retina.

Fig. 36-9 Vertical lines are imaged in front of this astigmatic eye.

Fig. 36-12 The diverging cylindrical lens images the vertical line on the retina of this astigmatic eye.

Fig. 36-10 (a) An uncorrected hyperopic (farsighted) eye. (b) A positive (converging) lens gives the extra convergence needed for a hyperopic eye to focus the image on the retina. The virtual image formed by the converging lens acts as an object at the near point.

Fig. 36-11 (a) An uncorrected myopic (nearsighted) eye. (b) A negative (diverging) lens spreads the rays so that the myopic eye can focus the image on the retina. The virtual image formed by the diverging lens acts as an object at the near point.

Fig. 36-13 The magnifier: (a) The subtended angle q (angular size) is largest when the object is at the near point. (b) The magnifier gives a virtual image at infinity. The virtual image appears to the eye to be a real object subtending a larger angle q at the eye.

Fig. 36-14 (a) Elements of a microscope. (b) Object is very close to the objective lens.

Fig. 36-15 Astronomical refracting telescope. Distant object has a real inverted image.

Fig. 36-16 Inversion of an image in prism binoculars.

Fig. 36-17 Optical systems for reflecting telescopes. (a) prime focus; (b) Newtonian; (c) Cassegrain.

Fig. 36-18 Spherical aberration for a lens. The circle of least confusion is shown by C.

Fig. 36-19 Astigmatism for a lens for a point below the optic axis. The lens forms two images of the point, in planes perpendicular to each other.

Fig. 36-21 Problem 36-39 Focal length of a zoom lens.