Chapter 36347Q36.8We assume the lens has a refractive index higher than its surroundings. For the biconvex lens inFigure 36.27(a), R10>and R20<. Then all terms in nRR−−FHGIKJ11112afare positive and f>0. For theother two lenses in part (a) of the figure, R1and R2are both positive but R1is less than R2. Then>and the focal length is again positive.For the biconcave lens and the plano-concave lens in Figure 36.27(b), R10<and R20>. Thenboth terms are negative in −and the focal length is negative. For the middle lens in part (b)of the figure, R1and R2are both positive but R1is greater than R2. Then <and the focallength is again negative.Q36.9Both words are inverted. However OXIDE has up-down symmetry whereas LEAD does not.Q36.10An infinite number. In general, an infinite numberof rays leave each point of any object and travel inall directions. Note that the three principal raysthat we use for imaging are just a subset of theinfinite number of rays. All three principal rays can
This is the end of the preview.
access the rest of the document.