A compound microphone has an objective of focal length 1 cm and an eyepiece of focal length 2.5 cm. An object has to be placed at a distance of 1.2 cm awy from the objective for normal adjustment. a.Find the angular magnification. b.Find the length of the microscope tube.

Explanation

a. If the first image is formed at a distance v form the objective we have
`1/v-1/((-1.2cm))=1/(1cm)`
or v=6cm
The angular magnification in normal adjustment is
`m=v/u D/(f_e)=-(6cm)/(1.2cm)=(25 cm)/(25cm)=-50.
b. for normal adjustment the first image mut be in the focal planeof the eyepiece.
the length of the tube is therefore
`L=v+f_e=6cm+2.5cm=8.5cm`.