Optical instruments are based on optical principles and are intended to facilitate the visualization of certain objects.
There is an infinity of optical instruments, we can mention: microscope, telescope, projectors, magnifying glass, photographic camera, glasses, lenses etc. See below how some of the optical instruments that are used in our daily lives work.
the human eye
It basically consists of three parts:
Crystalline : Works like a biconvex lens. It is situated in the anterior region of the eyeball;
Retina : located at the “background” of the eyeball and functions as a light-sensitive shield;
Optic nerve : part that receives light sensations received by the retina.
When we look at an object, the image is perceived by the lens, which forms a real and inverted image, that is, “upside down”. This image must be focused exactly on the retina in order to be seen clearly. The image is “sent” to the brain via the optic nerve. The brain, upon receiving the image, processes its inversion, so that we can observe the object in its real position.
The main parts of the human eye
If the image received by the lens is not formed exactly on the retina, then the person will not see objects clearly, which characterizes a vision defect. According to the position where the image is formed, we can classify three types of vision defects. Are they:
Myopia : the image of the object forms before the retina, as the eyeball of people who have this defect is more elongated. In this case, the person sees objects without sharpness. To correct the problem, it is necessary to wear glasses with diverging lenses.
Presbyopia : Popularly called “tired view”, it is a problem that occurs due to the natural aging of our body, when the lens becomes more rigid and does not accommodate images of nearby objects. In this case, the image forms behind the retina. This problem can also be corrected by converging lenses.
It is an optical instrument that projects and stores an image onto a screen and works similarly to the human eye. It has a lens system, called objective, which behaves like a converging lens and forms a real and inverted image of the photographed material. In order for the image to be clear on the photographic film, the camera has a series of systems that bring the lens closer or further away, focusing the image.
If this focus is not done well, the image will not form on the film and, therefore, will not be sharp. When the photo button is pressed, the camera’s diaphragm is opened, allowing light from the object to fall on the film. As photographic film is made of a light-sensitive material, it will “record” the received image.
the magnifying glass
It is the simplest optical instrument, consisting of a converging lens that produces a virtual and magnified image of an object.
For the image formed by the magnifying glass to be clear, it is necessary that the object is placed between the focus F and the optical center. Otherwise, the image is blurred.