Optical Instruments Problem Set - Draft only

problems not yet vetted

1. Find the power and the focal length of the following lens, when placed in close combination. f₁=20 cm, f₂=-60 cm, f₃=40 cm. (ans. f=17.2 cm, P=5.8 diopter)
2. A magnifying glass creates an image of the sun, 3.0 cm from the centre of the lens. What is the power of the lens? (ans. P=8.33)
3. In a simple microscope, the objective has a 3.0 cm focal length and the eyepiece has a 5 cm focal length. What is the magnifying power of the microscope?
4. A student makes a simple microscope by cementing a 5.0 focal length lens to the end of a 10 cm long tube and a 3.0 cm focal length lens to the other.
   1. If the student uses the 3.0 cm lens as an eyepiece, How far in front of the objective lens must the specimen be placed? (ans. 16. cm)
   2. What will be the approximate power of the microscope? (ans. P=4.2 diopter)
5. A telescope has an objective lens with a focal length of 62 feet. When observing the moon, how many miles on the moon corresponds to 1 inch of length on the image, cast by the objective lens? dist. to moon 2.4 x10⁵ miles. 5280 feet in a mile, 12 inches in a foot.
6. What is the magnifying power of a telescope,having a 1.0 diopter objective and a 20 diopter eyepiece?