Question

2. In a compound microscope, the focal length of the objective lens is 5 cm. 1 mm tall object is placed 7 cm in front of the objective lens and the eyepiece is focused so that an inverted image is formed 8 cm in front of the objective lens. The distance between the objective lens and the eyepiece is 30 cm. (Hint: Draw a rough diagram and indicate the length measurements as described above) (a) Determine the focal length of the eyepiece (b) What it the total magnification of the image

Answer 1

a)

$F=\frac{fd}{f+d}=\frac{8\cdot 7}{8+7}=3.7~cm,$

$F=\frac{F_1F_2}{F_1+F_2-\Delta},\implies$

$F_2=\frac{F(\Delta-F_1)}{F_1-F}=\frac{3.7\cdot(30-5)}{5-3.7}=71.2~cm,$

b)

$\Gamma =\frac df(1+\frac{F_2}{F_1})=17.4.$