a. What is the instrument shown above? b. What additional optical modification is usually incorporated for ophthalmic uses? c. Supposing the the objective lens is 40D, L is 20cm and the eyepiece is 10D. What is the total magnification?

b. What additional optical modification is usually incorporated for ophthalmic uses?

c. Supposing the the objective lens is 40D, L is 20cm and the eyepiece is 10D. What is the total magnification?

Answer to aA compound microscope. Answer to b A Porro's prism. The image is inverted both horizontally and vertically. A Porro's prism is used to invert the image to make it upright. Answer to c 20X A compound microscope uses a very short focal length objective lens to form a greatly enlarged image. The image is then viewed with a short focal length eyepiece used as a simple magnifier. The following formula can be used to calculate the magnification. M = mo (me) M = total magnification mo = linear magnification = L/fo (focal length of the objective lens) = 0.2/0.025 = 8 me = angular magnification = Fe/4 = 10/4 = 2.5 M = 8(2.5) = 20

Answer to b A Porro's prism. The image is inverted both horizontally and vertically. A Porro's prism is used to invert the image to make it upright.

Answer to c 20X A compound microscope uses a very short focal length objective lens to form a greatly enlarged image. The image is then viewed with a short focal length eyepiece used as a simple magnifier. The following formula can be used to calculate the magnification. M = mo (me) M = total magnification mo = linear magnification = L/fo (focal length of the objective lens) = 0.2/0.025 = 8 me = angular magnification = Fe/4 = 10/4 = 2.5 M = 8(2.5) = 20