Compound microscope: It is an optical device used to see highly magnified image of tiny objects.
Construction: It consist of two convex lenses of short focal length arranged co-axial at the free end of tube, at a suitable fixed distance.
When the final image is formed at the least distance of distinct vision:
The objective lens forms a real, inverted and magnified image A’B’ of the object AB on the other side of lens.
The distance between the objective and eyepiece is so adjusted that the image A’B’ lie within the focus of eyepiece.
This image A’B’ acts as an object for eyepiece.
The eyepiece E form a virtual and magnified final image A”B” which is inverted to object.
Magnifying power: The ratio of the angle subtended by the eye by the final virtual image, to the angle subtended at the eye by the object
h’ =height of image, h = height of object
The eye piece acts as a simple microscope.
where D = distance between eye piece to final image
Case II: When the final image is formed at infinity
When A’B’ lie on focus of eye piece.
so final image A”B” is formed at infinity.