p35_010 - 10. (a) f = +20 cm (positive, because the mirror...

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10. (a) f = +20 cm (positive, because the mirror is concave); r =2 f =2 (+ 2 0cm )=+ 4 0cm ; i = (1 /f 1 /p ) 1 =(1 / 20 cm 1 / 10 cm) 1 = 20 cm; m = i/p = ( 20 cm / 10 cm) = +2 . 0. The image is virtual and upright. The ray diagram would be similar to Fig. 35-8(a) in the textbook. (b) The fact that the magni±cation is 1 and the image is virtual means that the mirror is flat (plane). Flat mirrors (and flat “lenses” such as a window pane) have f = (or f = −∞ since the sign does not matter in this extreme case), and consequently r = (or r = −∞ ) by Eq. 35-3. Eq. 35-4 readily yields i = 10 cm. The magni±cation being positive implies the image is upright; the answer is “no” (it’s not inverted). The ray diagram would be similar to Fig. 35-6(a) in the textbook. (c) Since f> 0, the mirror is concave. Using Eq. 35-3, we obtain
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