Question

Explain the construction and working of a ‘Compound Microscope’.

With the help of a ray diagram, describe the construction and working of a compound microscope.

Answer 1

Construction:

1. A compound microscope consists of two convex lenses. The lens with the shorter focal length is placed near the object, and is called an ‘objective lens’ or ‘objective piece’.
2. The lens with a larger focal length and larger aperture placed near the ‘observer’s eye is called an ‘eye lens’ or ‘eyepiece’.
3. Both lenses are fixed in a narrow tube with an adjustable provision.
   
   Image formation in a compound microscope

Working:

1. The object (AB) is placed at a distance slightly greater than the focal length of the objective lens (u > f₀).
2. A real, inverted, and magnified image (A’B’) is formed at the other side of the objective lens.
3. This image behaves like the object for the eye lens. The position of the eye lens is adjusted in such a way that the image (A’B’) falls within the principal focus of the eyepiece.
4. This eyepiece forms a virtual, enlarged, and erect image (A” B”) on the same side of the object.
5. A compound microscope has 50 to 200 times more magnification power than a simple microscope.