When object is at do, lens must create cm - 50 cm f an (virtual) image at -dnear. Two people who wear glasses are camping. One of them is nearsighted and the other is farsighted. Which person"s glasses will be useful in starting a fire with the sun"s rays? Two people who wear glasses are camping. One of them is nearsighted and the other is farsighted. Which person"s glasses will be useful in starting a fire with the sun"s rays?