A concave mirror has the focal length equal to 0.491 m. To form a real image that is triple the size of the object on a screen, at what distance in front of the mirror should the screen be placed (in In; answer a positive number)? QUESTION 17 The gure shows an object and its image formed by a mirror. Assume that d1 = 0341 m, 0'; = 0.478 m, and 17 = 7.50E-2 in. What is the focal length of the lens (in In; answer sign and magnitude)? 0'2 d1 Qyqp h 9 Optic Object ax1s Image Mirror QUESTION 18 The gure shows an object and its image formed by a mirror. Assume that d1 = 00378 In, d3 = 0.761 in, and 17 = 7.50E-2 m. What is the image height (in In; answer sign and magnitude)? h _ 9 Optic Object . 3x15 Mirror Image