What kind of lens does the image give: examples

To understand which lens gives what kind of image, you first need to remember what a lens is. The main physical phenomenon that is used to create a lens is the refraction of light passing through the medium. It is this phenomenon that made it possible to create such an instrument that can control the direction of light fluxes. The principles of such management are explained to children even at school, in the course of physics of the eighth grade.

The definition of the word lens and the material that is used to make it

Lenses are used to enable a person to see an enlarged or reduced image of an object. For example, using a telescope or a microscope. Therefore, this device is transparent. It is done with the purpose to see objects as we are in reality, only changed in size. It will not be colored, distorted, if it is not required. That is, the lens is a transparent body. Next, we turn to its components. The lens consists of two surfaces. They can be curved, often spherical, or one of them will be curvilinear, and the second one will be flat. It is from these planes that which lens gives which lens depends. Material for making lenses in a wide range of everyday life is glass or plastic. Next, we will talk about glass lenses for a common understanding.

Separation into convex and concave lenses

This separation depends on the shape of the lens. If the lens has a middle wider than the edges, it is called convex. If on the contrary - the middle is thinner than the edges, that such a device is called concave. What else is important? The important thing is in what environment is the transparent body. After all, what kind of lens which image gives, depends on the refraction in two environments - in the lens itself and in the surrounding matter. Next we will consider only airspace, since the refractive index of the lens from the glass or from the plastic is higher than the established index of the environment.

Collecting lens

We take a convex lens and let through it a stream of light (parallel rays). After passing through the surface plane, the flow is collected at one point, because the lens is called collector.

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

Important parameters for understanding the properties of this glass body

If the lens is bounded by two spherical surfaces, then its spheres, of course, have a certain radius. These radii are called the radii of curvature that come out of the centers of the spheres. The straight line that connects both centers is called the optical axis. A thin lens has a point through which the beam passes without any deviations from its previous direction. It is called the optical center of a lens. Through this center, perpendicular to the optical axis, a perpendicular plane can be drawn. It is called the main plane of the lens. There is also a point called the main focus - the place where the rays will gather after passing the glass body. When analyzing the question of what image the collecting lens gives, it is important to remember that its focus is on the reverse side of the entrance of the rays. At the scattering lens, the focus is imaginary.

What image of the object does the collecting lens give?

This directly depends on the distance at which the object is placed relative to the lens. There will be no valid image if you place an object between the focus of the lens and the lens itself.

The image is imaginary, direct, and significantly enlarged. An elementary example of such an image is a magnifying glass.

If you place objects behind the focus, then two options are possible, but in both cases the image will be inverted and valid first. The difference is only in size. If you place objects between the focus and the double focus, the image is enlarged. If you place it behind a double focus, it will become smaller.

In some cases, it may happen that no image will be received at all. As can be seen from the figure above, if you place the object just in place of the focus of the lens, the lines intersecting which gives the top point of the object run parallel. Accordingly, there can be no question of intersection, because the image can only be obtained somewhere in infinity. Also interesting is the case when an object is placed in the place of a double focus. In this case, the image is turned upside down, real, but the size is identical to the original object.

In the figures, this lens is schematically depicted as a segment with arrows at the ends directed outward.

Dispersing lens

Logically, the concave lens is dissipative. Its difference is that it gives an imaginary image. The rays of light after its passage are scattered in different directions, because there is no real image. The answer to the question of what kind of image the scattering lens gives is always one. In any case, the image will not be inverted, that is, straight, it will be imaginary and reduced.

In the figures, this lens is schematically depicted as a segment with arrows at the ends that look inwards.

What is the principle of image construction

There are several steps for building a collective lens . The object, the image of which will be built, has a top. From it you need to draw 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 that is needed is to connect the optical axis and the resulting point, parallel to the original object. In the case where the object is in front of the focus of the lens, the image will be imaginary and will be on the same side as the object.

We remember which image the scattering lens gives, so we are building an image for a concave lens, on the same principle, with only one difference. The focus of the lens used to build is on the same side as the object whose image you want to build.

conclusions

We summarize the above materials, in order to understand which lens which image gives. It is clear that the lens can increase and decrease, but the questions are different.

Question number one: which lenses give a valid image? The answer is only collective. It is the concave collective lens that can give a real image.

Question number two: which lens gives an imaginary image? The answer is dissipative, and in some cases, when the object is between the focus and the lens, it is collective.