Optical instruments are devices that are used for the enhancement of the images of the object. Anything as simple as a magnifying glass fitted with a convex lens is also an optical instrument. These days we have even complex combinations of lenses that use a very basic phenomenon of optics but have beautiful applications. Through this article, we shall learn about its significance, types, and how they are used in various areas of research as well as in day-to-day lives.
Optical instruments, or can be called just ‘optic’ in short form, are the devices that process the light for an enhanced image of the object. Other than just enhancing or clarifying the image for viewing, they can also be used to analyze the characteristics of the light. The usage of some instruments for magnification was seen back since Galilieo, known as the Father of Observational Astronomy, used to work with telescopes for the magnification of distant planets.
Telescopes are known to be one of the very first optical instruments to be made. The optical instruments use very basic phenomena of light- refraction, and reflection to produce the images. Refraction is the phenomenon of bending the light while passing from one medium to the other. Optical lenses and mirrors are usually used in different combinations for the same. The convex lenses, being diverging in nature, are used to make an enlarged image of the object. Whereas the concave lenses, being converging in nature, are used to make smaller images of the object.
The net magnification power of an optical instrument can be defined as the ratio of the angle (known as the visual angle) subtended by the image formed, on the eye of the human to the angle subtended by the object seen directly without the instrument. Both image and object should be at the nearest point of the vision while considering the angle subtended. It is also known as the angular magnification, often denoted by M. Mathematically, it can be written as −
$$\mathrm{Angular\:Magnification\:M=\frac{Angle\:subtended\:by\:final\:image\:on\:the\:eye(\beta )}{Angle\:subtended\:by\:the\:object\:on\:the\:eye(\alpha )}}$$
While we discussed the visual image angle included in the magnification of definition, let's have a little deeper insight into what it refers to in optics. The Visual Angle is the angle subtended by the object on the human eye. A larger visual angle pimples larger objects, and similarly the smaller angle implies a smaller object size. Hence, the work of the optical instrument is to increase the visual angle for our eyes so that we perceive a bigger size of the image, hence enhanced and magnified.
We have already discussed what a basic optical instrument consists of and what work it was expected to do since it was initially invented. But now that we talk of the modernday to day applications or their importance in research, it is almost impossible to imagine our lives without optics and optical instruments.
For instance, we cannot just forget the case of the human visual system, our eyes, while mentioning the importance of the optical instruments. Our eyes, which make the ultraclear HD images in our mind for whatever we see, form a natural setup of an optical instrument. For the objects at different distances, it creates a large view of objects with high resolution at the center of the retina, and all of this is done by the natural tissues and lenses fit inside our body.
Another important application of the optical instrument that we see today is an optical fiber for carrying communication signals. Important information, audio, and pictures are coded into pulsated signals and made to be incident on one end of the optical fiber. The fiber uses the concept of total internal reflection and transfers the signal with absolutely no or very less loss through the journey. All of the signal/ wave is reflected off the inside of the fiber, so none of it escapes. Optical fibers are used to carry telephone, cable TV, and Internet signals. Other than this, there are various other examples, like a camera, high-resolution microscope, telescope, etc, where the optical instruments have proved their importance for not only image enhancement but also in unveiling various characteristics of the light.
The major types of the optical instruments that are commonly in use these days can be listed as follows −
Camera− It is a widely used optical instrument that is capable of capturing images and recording. The light passes through the opening called the aperture in the front. A reduced real image is formed as the light further passes through the lens. Focus can be adjusted by changing the position of the lens.
Microscope − A light microscope is an optical instrument used for making magnified images of objects that are too small for the naked human eye to see. The compound microscope is one of the types of light microscope which uses at least two convex lenses: eyepieces and objective lenses. The objective lens is placed close to the object whereas the eyepiece lens is close to the eye of the observer. Some microscopes invented have the potential to magnify objects even more than 1000 times.
Telescopes − Telescopes are used to make magnified images of far-away objects, such as stars and planets, that aren’t small but they appear small because of being too far from our eyes. Like microscopes, telescopes also use convex lenses to make magnified images.
Periscopes − A periscope is a device to observe around, over, or through an object. In other words, it is useful for the circumstances whenever there is no possible direct line of sight. for observation from the position of the observer. It consists of the two plane mirrors that are placed parallel to each other at a 45$\mathrm{^{\circ}}$ angle horizontal.
Kaleidoscope − A kaleidoscope is an optical instrument that consists of two or more plane mirrors tilted and joined at some angle. A regular symmetrical pattern is created as the objects as well as the images act as the object again for the next reflection. When viewed from the other end, due to repeated reflection, beautiful patterns can be seen.
Optics is a study of light and further, with the help of the optical instruments it allows us to see the world in a better way. From image magnification, enhancement, and analyzing the behavior of the light wave, to the modern communication system of optical fibers, optical instruments have given the world today a lot.
Q1. Name an optical instrument that produces a virtual image?
Ans. Microscope
Q2. Do the optical fibres have lenses fitted inside them?
Ans. No. They just use the phenomenon of total internal reflection. While the optical fiber lights can have a lens fitted at the end for spreading light over a larger area, they do not have a lens fitted inside them for functioning.
Q3. What will happen if a microscope constructed has no mirror in it?
Ans. Mirrors in the microscopes reflect the light coming from the source to the object. However, a light bulb can be used in place of a mirror and that can behave like the light source.
Q4. Explain briefly the construction of a binocular?
Ans. Binocular is an optical instrument that consists of an objective lens and the eyepieces with two facings, and right-angle prisms.
Q5. Name two kinds of telescopes?
Ans. The two kinds of telescopes are: Reflecting telescopes and refracting telescopes. They both have convex lenses to form enlarged images but differ in how they collect light.
Physics
Biology
Chemistry
Mathematics
Economics
Psychology
Environmental Science
Social Studies
Fashion Studies
English