ANSWERS TO EXAMPLES CHAPTER II (p. 129) 5. As 4 is to 9. 6. As 9 is to 4. 7. 10.24 candle-power. 8. I ft. from the candle and 3 ft. from the lamp. CHAPTER V (p. 167). = 3. The image would be formed 1 ft. 4 in. in front of the mirror. 4. 6 cm. behind the mirror. 5. f= +30 cm.: the mirror is concave. 6. The image is 7 ft. 6 in. in front of the mirror and is 5 in. long. 7. f= +12 cm.: the mirror is concave. 8. The image is 3 ft. from the mirror and 3 in. long. 9. The image is 10 in. in front of the mirror and 2 in. high. 10. ƒ +8 in. 11. p: +18 in.; p= +36 in. The image would be one-half the size of the object. 12. Real, 33 cm. in front of the mirror, and 4 cm. long. 14. 30 in. behind the mirror; magnification = 6. 15. The image moves through 3.7 in.; i.e. from 24 in. behind the mirror to 20.3 in. behind it. 17. (1) Image is virtual and erect, 4 in. behind the mirror, 2 in. long; (2) image is 8 in. behind the mirror, I in. long. 18. The image is 7.5 cm. behind the mirror and 3 cm. long. CHAPTER VII (p. 210) 1. Convex: f= − 3 in. 2. 36 cm. behind the lens. 3. They converge to a point 5 cm. from the lens and on the other side. 4. 3 ft. from the lens on the other side. 5. Image is real, 6 = in. long and 63 in. from lens. 6. p' of object. 7. 10 cm. 8. 2 ft. 6 in. - 2 ft. diameter of image = 1 in. 20 cm. one-third size equal in size. 9. p= 11. I ft. from the lens and on the same side as the object. 12. ƒ= - 37.5 cm. ; as 3 to I. 13. The object must be 1 ft. from the lens and the image 3 ft. (on the opposite side). 14. p' = + 12 in.; ƒ= – 10. in. 10 in. 15. (1) 2 ft.; (2) p 1 ft. 16. = - |