Chapter 25, Problem 36P

Galileo’s telescopes, I. While Galileo did not invent the telescope, he was the first known person to use it astronomically, beginning around 1609 Five of his original lenses have survived (although he did work with others). Two of these have focal lengths of 1710 mm and 980 mm. (a) For greatest magnification, which of these two lenses should be the eyepiece and which the objective? How long would this telescope be between the two lenses? (b) What is the greatest angular magnification that Galileo could have obtained with these lenses? (Note: Galileo actually obtained magnifications up to about 30×, but by using a diverging lens as the eyepiece.) (c) The moon subtends an angle of 0.5° when viewed with the naked eye. What angle would it subtend when viewed through this telescope (assuming that all of it could be seen)?