Question

Explain the construction and working of a compound microscope with a neat ray diagram.

Answer 1

Hint: Firstly you could make a neat ray diagram consisting of the basic components of a compound microscope, marking all the necessary quantities. Then, you could list explain the working by discussing the image formations involved in it. Thereby, you will make a brief note how a compound microscope forms a magnified, inverted and virtual image.

Complete answer:
In the question, we are asked to explain the construction and working of a compound microscope with the help of a neat ray diagram.

Firstly let us discuss the construction of a compound microscope. A compound microscope basically consists of two lenses. That lens that we keep towards the object called the objective lens and the other that we keep near our eye called the eyepiece. These lenses are chosen in such a way that the focal length of objective lens is smaller than that of eye piece, that is,
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Such a combination of lenses assures us the magnified image of the object that is kept in front of the objective lens when viewed through the eyepiece.

Now let us discuss the working of a compound microscope. Consider an object AB that is kept at a distance greater than the focal length of the objective lens. Image A’B’ of this object so obtained is real, inverted as well as magnified and is formed at a point beyond the centre of curvature of the objective lens. Now this image A’B’ acts as the object for eyepiece. So, the eyepiece now forms a virtual, erect and magnified image A”B” of the object A’B’. So the final image formed by the compound microscope will be virtual, inverted and magnified at a point behind the point at which the object is kept.

Note:
While discussing the working, we have formed the image by using the basic rule that we use for lenses. The object is kept between the centre of curvature and focal point and the image so formed is beyond C. Now for the eyepiece this image acts as an object and the corresponding image is found to be virtual, erect and magnified. This image is the final image, but with respect to the observer the final image is virtual, inverted and magnified.