lens It is a permeable device optics Focuses or distracts optical rays by property Refraction of Light. made up The simple lens from one piece transparentwhile consisting compound lens consists of several simple lenses (“elements”), usually arranged along a common longitudinal axis known as a lens in the optical axis. Lenses are made of different materials the glass or plasticsWhich leveled and polished or Formed by the casting process As required. The lens can focus light to form picture In contrast Prism through which light is refracted without focus. Devices that similarly focus or scatter waves and radiation other than visible light are also called lenses, such as bifocal lenses microwaves, and window electron microscopes, and acoustic lenses, and explosive lenses.

Lenses are used in many imaging devices such as telescope And binoculars And the photocopier. It is also used as visual aids the glasses To correct vision defects such as: Nearsightedness and farsightedness.

Types of simple lenses[عدل]

Most lenses are spherical lensesA lens consists of two surfaces, each of which is part of a surface a balland so that is lens axisi.e. the straight line connecting the centers of the two spheres, vertically on both surfaces. And according to how the light is refracted and passed through the lens and the quality of the resulting images, it is described as a convex (collective) or concave (dispersed) lens.

There is also another type Aspherical lensesThese are lenses in which one or both surfaces are not spherical or cylindrical. Some of these lenses can produce sharper images with less aberrations than spherical lenses. We single out the biplane-shaped lens Parabolawhich makes a bundle of parallel light rays on one side converge at exactly one point on the other side, namely focus. It is often more expensive to manufacture such lenses than spherical lenses.

convex lens They are optical means of refraction the light while passing through it, and are made of transparent, azeotropic materials like glass, and it has spherical surfaces where the surface of the lens is either equal or different in curvature, according to the purpose for which the lens is used, and the convex lens also has a real focus, because it results from the gathering of reflected rays, and its focal length is often 5 cm. The line joining the two centers of curvature in a single lens is known as the “axis of the lens.”

Concave lens The lenses are concave or convex in one or both of their surfaces. The rays are focused in the form of a focus, where they are refracted rays optical falling on one of her faces. A convex lens is used to focus light rays. While the concave lens is used to disperse the rays, the concave lens also has an imaginary focus, because it dispersed the light and received it behind the mirror. A concave lens shows vision from afar, but not close up break in camera rays the light towards the outside, so the rays then appear as if they were coming from a smaller image or closer to the camera than they are in reality. The concave lens also helps near-sighted people see distant objects, as the concave lenses refract the light rays outward, so that distant objects appear close to the eye.

The actual path of the rays through the lens (whether it is cloaking or diffusing) depends on its shape, and the two main types of lenses are convex lenses And the concave lenses, and the convex lenses are your name in the middle of them in their edges, while the concave lenses are your name in their edges than in the middle of them.

If a beam of parallel rays of light falls on a convex lens, it converges at approximately one point lens focus Convex, but if this beam falls on a concave lens, it disperses as if it were issued by a discretionary focus of the lens. In both cases, it is called the distance between the center of the lens and the focus by focal length Which is considered positive in the convex lens and negative in the dividing lens.

Lens polishers law[عدل]

can be calculated Focal Length for a spherical lens Up in the air by Lens polishers law:

${\displaystyle \frac 1f=({\frac n_1n_2))-1)\left[\frac 1R_1-\frac 1R_2+\frac (n_1-1)dn_1R_1R_2\right],$

So that:

$\displaystyle f$

is the focal length of the lens,

$\displaystyle R_1$

he radius the spherical surface closest to the light source,

$\displaystyle R_2$

he radius The spherical surface farthest from the light source,

$\displaystyle n_1$

he refractive index The light in the lens material

$\displaystyle n_2$

he refractive index light in the substance surrounding the lens f

$\displaystyle d$

is the thickness of the lens.

In the above law:

• If the first surface is convex it is considered
  $\displaystyle R_1$

  Positive, and considered negative if the surface is concave

• And vice versa for the second surface: it is positive for a concave surface, and negative for a convex surface
• If one of the two surfaces is flat, then its radius is considered No final

The law can be simplified if the lens is accurate, that is, if

$\displaystyle d$

small for

$\displaystyle R_1$

And

$\displaystyle R_2$

:

${\displaystyle \frac 1f=({\frac n_1n_2))-1)\left[\frac 1R_1-\frac 1R_2\right],$

called value

${\displaystyle {\frac 1f))$

Lens power, measured in units diopters which is equivalent to (metre¹⁻). The power of the lens is characterized by its ability to “fold” a beam of parallel light rays. The stronger the lens, the smaller its focal length, meaning its ability to make the beam refracted is stronger.

For each lens, the focal length remains the same regardless of which side of the lens the light source is on. However, other properties of lenses, such as the extent of different aberrations they cause, may be different if the light is directed differently.

Micro lens law[عدل]

The lens has photographic properties. For example, if a converging lens is placed in the path of a parallel beam of light rays, all of them converge at one point on the other side of the lens, which is the focus of the lens. Conversely, if a light source is placed at a point that is the focus of a convergence lens, the rays exit from the lens in the form of a parallel beam of light rays. The first case describes an object that is very far away, to the extent that the rays that reach the lens from it are parallel, and its image is formed in focus, and in the second case, an object standing at a focal distance from a lens, its image is formed at infinity. The plane perpendicular to the axis of the lens and far from it is called a distance fhe claims focal plane.

If we put an object at a distance u of a lens its focal length is fAnd if we consider the distance from the lens in which the image is formedvthen the following named relation is achieved Micro lens law:

${\displaystyle \frac 1f=\frac 1u+{\frac 1v))$

So, if we put an object at a distance u is greater than the focal length of the lens,fwe get a positive value ofvie that The picture is real It consists of the other side of the lens. This means that it is possible to bring a screen and install it from a distance v From the lens and we can then see the image of the object (magnified or reduced), and this is the basis of the process Photography.

As for if it is a value u smaller than the value fit will be valuable v Negative, that is, the image is formed on the same side as the body, and then it is called dummy imagesimilar to that which we obtain when considering Mirror flat. Contrary to the real image, it is not possible to set up a screen until we see the imaginary image on it, but if we look at the object through the lens, we can see that image at a distance v From the lens, this is the basis of work magnifying glass.

can calculate zoom range lens, M By the law of similar triangles:

${\displaystyle M=-\frac vu={\frac ffu))$

Where is the reference M Indicates whether the image is upside down or not. if it was

$>1$

, the image is larger than the object, that is, we get an enlargement. If an imaginary image is formed, the magnification is always positive, i.e. the image is not inverted with respect to the object.

The above rules also apply to diverging lenses, with a sign reserved f Negative of these lenses. A real image cannot be formed by means of a diverging lens, all images are illusory, ie

$\displaystyle v<0$

uses[عدل]

A convex lens is used as a magnifying lens. If an object is placed between the lens and its focus, the viewer on the other side of the lens sees an enlarged image of the object at a distance greater than the actual object’s distance from it. But if the object is placed at a distance from the lens that exceeds its focal length, you will not see any image of it. But you can get a real image of it (upside down) on a piece of paper or a curtain on the other side of the lens. Especially if the object is luminous or well-lit, but in the case of the concave lens, it is the opposite, as it is used to reduce the image, as the concave lens forms a moderately estimated image of the object (not inverted) miniaturized and on the same side as the object.

human eye[عدل]

contains Eye Humanity convex lens Adapted to group incoming rays across pupil on me retina in the background of the eye. It may happen sometimes in some people that the lens of the eye collects light rays at a point in front of the retina, and this condition is called nearsightedness. In other cases, in some people, the lens of the eye collects light rays behind the retina, and this condition is called farsightedness (or farsightedness). Both cases are treated in several ways, including the use of the glasses or Contact lenses or eyelid surgery. Also, there is a so called with astigmatism And treatment with cylindrical lens or with a laser.

See also[عدل]

References[عدل]

external links[عدل]

• optics
• Lenses and mirrors
• Lenses and refraction
• lenses and clarity
• Calculation of lens thickness

• Optics portal
• Physics portal

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