A mirror . It is a smooth and polished surface capable of reflecting the light it receives. There are flat mirrors and spherical mirrors. The planes form symmetrical images of the objects. The spherical ones give deformed images.
A lens . It is a transparent medium, limited by two spherical surfaces or by one spherical and one flat. There are converging lenses and diverging lenses. Converging lenses bring light rays together at one point. The divergent ones separate them. Lenses are used to manufacture glasses , magnifying glasses , binoculars , projectors .
[ hide ]
- 1 Chronicles
- 2 kinds of mirrors
- 3 Images in the flat mirror
- 4 Images in the spherical mirrors
- 5 Lenses
- 6 kinds of lenses
- 7 Mirror and lens applications
- 8 glasses or contact lenses
- 9 Magnifying glass
- 10 Source
Man has used the behavior of light in its propagation to build objects and instruments that are useful to him. Such is the case of mirrors and lenses.
Mirror is any smooth, polished surface capable of reflecting the light it receives. In ancient times, mirrors were made from well- polished metals ; the famous Etruscan mirrors were made of bronze . Glass was used as a mirror in the 15th century , after covering it on one side with a tin amalgam. Later, this amalgam was replaced by silver salts .
Depending on the way of behaving before or reflecting light, several types of mirrors are distinguished:
- Flat mirrors: its surface is flat.
- Spherical mirrors: its surface is that of a spherical cap or sphere portion. Two types of spherical mirrors are distinguished:
- Concave, if the polished surface is inside the cap.
- Convex, if the polished surface is the outside of the cap.
Images in the flat mirror
- When you stand in front of a mirror, there is you and your “double” image.
- Flat mirrors form symmetrical images of objects. The mirror is the plane of symmetry.
Images in spherical mirrors
Spherical mirrors distort the image; for this reason they are frequently used at fairs and some “”.
Lens is a transparent medium, limited by two spherical surfaces or by one spherical and one flat.
There are two fundamental types: convergent and divergent:
- The converging ones are wider at the center. The light rays passing through them meet at a point called focus.
- The divergent ones are narrower at the center. The rays of light that pass through them separate; diverge.
Mirror and lens applications
The main application of mirrors and lenses is the manufacture of optical instruments. These are intended to improve the perception of the images, either because they are very small or because they are very far away. The main optical instruments are:
Glasses or contact lenses
Two very common vision effects are nearsightedness and farsightedness .
- Myopia consists of seeing well near objects and badly far away. This defect is corrected with diverging lenses.
- Hyperopia is the opposite defect to myopia. It is corrected with convergent lenses.
The magnifying glass is a converging lens that, located between the eye and the object, allows us to see invaluable details with the naked eye.
When looking with a magnifying glass, the object must be placed between the focus and the magnifying glass so that the formed image is larger and on the same side where the object is.