What gives the image a lens: examples

To understand what a lens which gives the image, you must first recall that such a lens.The main physical phenomenon that is used to create the lens - is the refraction of light passing through the medium.This phenomenon has created a device that can control light direction.The principles of such management explained to children at school in the eighth grade physics course.

definition of the word, and the lens material used for its manufacturing

lenses are used to see the man was able to zoom in or out of an object.For example, using a telescope or a microscope.Therefore, this device is transparent.This is done with the aim to see things for what we really are, only a change in size.It will not be colored, distorted, if it is required.That is the lens - a transparent body.Then go to its constituents.The lens has two surfaces.They can be curved, often spherical or else one of them will be curved and the second plane.It depends on these planes is what gives the image a lens.The material for a lens in a wide life are glass or plastic.Then we speak about glass lenses for common understanding.

Separation of convex and concave lenses

This separation depends on what kind of lens shape.If the lens has a middle wider than the edge, it is called convex.If on the contrary - the middle is thinner than the edge that such a device is called concave.What matters more?It is important that the environment in which the body is transparent.After all, what gives the image a lens depends on the refractive index in the two environments - in the lens itself and the surrounding matter.Next, we consider only the air space, as the index of refraction of the lens from the glass or plastic is higher than the rate set by the environment.

collecting lens

Take a convex lens and pass through it a stream of light (parallel rays).After passing through the plane of the surface of the flow going at one point, because the lens is called collect.

To understand what gives the image collecting lens, and any other, you need to remember about the main parameters.

Important parameters for understanding the properties of the glass body

If the lens is bounded by two spherical surfaces, its scope, by itself, have a certain radius.These are called radii of curvature radii that come out of the centers of the spheres.The line that connects both centers is called the optical axis.In a thin lens is the point through which the beam passes without any deviation from its previous trend.It is called the optical center of the lens.Through the center perpendicular to the optical axis can be performed perpendicular to the plane.It is called the principal plane of the lens.Also, there is a point, which is called the main focus - a place where gather rays after passing through the glass body.In the analysis of the issue, which gives an image collecting lens, it is important to remember that its focus is on the reverse side of the entry of light.In the diverging lens focus is imaginary.

What is the image of the object gives the collecting lens

It depends on how far away the object is located relative to the lens.There will be no real image by placing objects between the focus lens and the lens itself.

The image is imaginary, direct, and greatly increased.The ultimate example of such an image - a magnifying glass.

If you place an item of focus, then there are two possibilities, but in both cases, the image will primarily be inverted and real.The only difference in size.If you place objects between the focus and dual focus, the image is enlarged.If the place of the dual focus, it will be reduced.

In some cases, it may happen that all will not be imaged.As you can see on the picture above, if you place the subject on the spot just focus lens line, which gives the upper intersection point of the object, go hand in hand.Accordingly, on the intersection can not be out of the question, because the image can get only somewhere in infinity.Also interesting is the case where the object is placed on the site of a double focus.In this case, the image is upside down, indeed, but is identical in size to the original object.

Figures this lens is schematically depicted as a segment with arrows at the ends outward.


Logically, concave lenses are diverging.It differs in that it provides a virtual image.The light beams after passing scattered in different directions, because there is no real image.The answer to the question of what kind of image gives diffuser, always alone.In any case, the image will not be upside down, that is right, it will be reduced and the imaginary.

Figures this lens is schematically depicted as a segment with arrows at the ends, which look inside.

How does imaging

Steps to building a more collective lenses.The object whose image is to be built, has a top.Because it is necessary to carry out two lines: one - through the optical center of the lens, the other - parallel to the optical axis to the lens, and then through the focus.The intersection of these lines will give the top of the image.All you have to continue - is to connect the optical axis and the resulting point parallel to the original subject.In the case where the object is in front of the focus lens, the image will be imaginary, and on the same side as the object.

We remember which image yields diverging lens, for imaging to conduct a concave lens on the same principle, but with one difference.The focus of the lens used for the construction, is on the same side as the object, the image that you want to build.


summarize the above materials, in order to understand which lens gives you a picture.It is clear that the lens can zoom in and out, but the question is another.

Question number one: What lens gives a real image?The answer - only collective.That collective concave lens can give a real image.

Question number two: What lens provides a virtual image?Answer - scattering, and in some cases, when the object is between the focus and lens - collective.