Physics 1102 In-Class Problems: Optical Instruments

1. The nearpoint of a farsighted person is 125 cm. What power contact lenses must this person wear to have "normal" vision?

2. If the person in Question #1 prefers glasses, what power should they be. Assume that the glasses are 2.00 cm from the eyes.

3. The farpoint of a nearsighted person is 8.00 cm. The person wishes to be able to read a newspaper held 50 cm away from the eye, what power contact lenses should the person wear?

4. If the person in Question #3 prefers glasses, what power should they be. Assume that the glasses are 2.00 cm from the eyes.

5. A photographer is taking pictures on a bright sunny day with a camera shutter speed of 1/250 s and f/5.6. Suddenly the sky clouds over and the available light is reduced by three-quarters. (a) If only the shutter speed is changed, what new shutter speed would be needed for proper contrast? (b) If only the f-number is changed, what new f-number is needed?

6. The separation of the lenses in a compound microscope is 18.0 cm. The objective and eyepiece have focal lengths of 0.20 cm and 3.00 cm, respectively. (a) What magnification would a person with normal vision observe? (b) Where would the object have to be placed?

7. Galileo's telescope had a magnification of 3×. Assuming that the focal length of the eyepiece was 15 cm, how long was his telescope?

Questions? mike.coombes@kwantlen.ca