Question

A microscope with a tube length of 180 mm achieves a total magnification of 800* with a 40* objective and a 20* eyepiece. The microscope is focused for viewing with a relaxed eye. How far is the sample from the objective lens?

Answer 1

Answer:

Given, tube length x = 180 mm = 18 cm, total magnification m = 800, magnification of eyepiece me = 20 = 25/fe and magnification of objective lens is mo = x/fo = 40, from this the focal length of the objective lens is fo = x/40 = 18 cm/40 = 0.45 cm.

The sum of the objective's focal length and the tube length gives the real image distance,i.e., image distance v = fo+x = 0.45 cm + 18 cm = 18.45 cm. Then we can calculate the object's distance u from the objective lens by using the lens formula,

1/fo = 1/u + 1/v

Therefore, the object's distance u = fo.v/(v - fo) = (0.45 cm)(18.45 cm)/ (18.45cm - 0.45cm) = 0.461 cm