33. Would the critical angle for a glass-water interface be less than, equal to, or greater than the critical angle for a glass- air interface? Explain your choice.

35. For transparent solids, distinguish between effects of surfaces that curve inward and those that curve outward on the paths of a parallel bundle of light rays incident on each.

37. If you were lost in the forest and wanted to start a small fire to keep warm or cook a meal using sunlight and a small lens, what type of lensconverging or divergingwould you use and why?

39. Describe the three principal rays used to locate an image.

41. Indicate whether each of the following is a real image or a virtual image. (a) Image on the retina in a person's eye (b) Image one sees in a rearview mirror (c) Image one sees on a movie screen (d) Image one sees through a magnifying lens

43. How is the magnification of a lens related to the object distance? How is it related to the image distance? What is the significance of the sign of the magnification? What is the significance of its magnitude (size)?

45. What is chromatic aberration? How can it be remediated?

47. When a person is nearsighted, what happens in the eye when the person is looking at something far away? How is this condition commonly corrected?

49. Two light waves that have wavelengths of 700 and 400 nm enter a block of glass (from air) with the same angle of incidence. Which has the larger angle of refraction? Why? Would the answer be different if the light waves were going from glass into air?

51. The difference in speed between red light and violet light in glass is smaller than the difference in speed between the same two colors in a certain type of plastic. For which material, glass or plastic, would the angular spread of the two colored rays after entering the material obliquely from air be the largest? Why?