In: Physics
Draw a schematic and clearly indicate the components of a compound microscope. In a compound microscope, why must the objective lens (or objective + Tube lens) be a converging lens (or lens system)?
From the physics point of view objective and eyepiece (convex) lensing systems are the main components in a compound microscope.
AB – Object
Fo – Focal length of objective lens
Fe – Focal length of eyepiece
A’B’ – image produced by objective lens and this image act as virtual object for convex lens of eyepiece.
A’’B’’ – a magnified, real, inverted and enlarged image of the sample of height AB in front of objective lens.
The objective lens must be converging or convex lens, because when the object is near to or inside the focal length of the (objective) convex lens, a magnified, virtual and erect image (A’B’) of the object is formed as in a simple microscope.
On the other hand if one use a diverging (or concave) lens as objective lens of a compound microscope, it produces a diminished image (A’B’) of the object (AB) according to the following ray diagram: