The limit of resolution of a microscope is the least distance between two point objects which can be seen clearly and distinctively with it. For a naked eye, limit of resolution is about `10^(-4)` m or 0.1 mm. The limit of resolution for a microscope is of the order of `lambda/2` , where `lambda` is wavelength of light used. For an optical microscope , using visible light, limit of resolution is `"500 nm"/2`=250 mm. This is 400 times smaller than naked eye. So the useful magnification produced by it is 400. Smaller is the limit of resolution, greater is the magnification that can be achieved. By using shorter wavelengths , we can improve resolution. For examination of a microorganism, much higher limit of resolution is needed, the Wave nature of electron provides a means for probes of very small size organisms. An electron beam accelerated by a high potential difference possess a very short wavelength. In an electron microscope magnetic lenses are used to control the path of electrons. The image of object is obtained on a fluorescent screen or on a photographic plate. The electron microscope with its high magnifying power and resolving power , is one of the most indispensable and powerful tool for research in science , medicine and industry. The advantage of electron microscope over optical microscope is thatA. It gives images which can be directly seen with naked eyeB. It gives a better resolution and magnificationC. It is very simple in its workingD. It uses magnetic lens in place of glass lens