Please explain the principle of concave lens and convex lens, please don't repeat it! thank you

Concave lens is also called negative spherical lens. The center of the lens is thin, the periphery is thick and concave, so it is also called concave lens. Concave lenses have a divergent effect on light. After the parallel rays are deflected by the concave spherical lens, the rays diverge and become divergent rays, and the real focus cannot be formed. Along the reverse extension line of divergent rays, they intersect at point F on the same side of the projected rays, forming a virtual focus. ?

The geometric drawing of concave lens imaging is the same as that of convex lens. From the top of the object, it is also regarded as two straight lines: one parallel to the main optical axis, deflected into divergent light after passing through the concave lens, and returned to the main focus in the opposite direction; The other line passes through the optical center of the lens, and these two straight lines intersect at one point, which is the image of the object. ?

The image formed by concave lens is always smaller than the vertical virtual image of the object, and concave lens is mainly used to correct myopia.

A transparent body with two spherical surfaces or one spherical surface and the other flat surface and a thin middle part is called a concave lens. When used in optical hydrophobic media, it can diverge the incident light beam, so it is also called divergent lens. Because its focal length is negative, it is also called a negative lens. For a thin concave lens, its imaging formula, lateral magnification formula and sign rule are the same as those of a convex lens. ?

There are three kinds of lenses: biconcave lens, plano-concave lens and convex-concave lens. The line connecting the curvature centers on both sides is called the principal axis, and the point o in the center is called the optical center. The light passing through the optical center will not be refracted no matter where it comes from. The light beam parallel to the principal axis is refracted on the concave lens and then diverges in all directions, and the extension line opposite to its divergence direction will all be at point F on the same side as the light source, and its refracted light will just emanate from point F, which is called virtual focus. One on each side of the lens. Concave lens is also called divergent lens. The focal length of a concave lens refers to the distance from the focal point to the center of the lens. The larger the radius of curvature of a lens, the longer its focal length. If it is a thin lens, the focal lengths on both sides are equal.

The image formed by concave lens is always smaller than the object.

Convex lens? Lens)

A convex lens is made according to the refraction principle of light. A convex lens is a kind of lens with a thick central part. Convex lenses are divided into biconvex, plano-convex, concave-convex (or positive meniscus) and other forms. Thin convex lens is also called condenser because of its convergence, while thick convex lens has telescopic and convergent functions, which is related to the thickness of the lens.

When parallel rays (such as sunlight) are parallel to the axis (the line connecting the spherical centers of two convex lenses is called the main optical axis of the lens), the rays are refracted twice at both sides of the lens and concentrated at a point on the axis, which is called the focus of the convex lens (marked F, English: Focus). A convex lens has a focal point on both sides of the mirror. If it is a thin lens, the distance between the two focal points and the center of the lens is approximately equal. The focal length of the convex lens refers to the distance from the focal point to the center of the lens, which is usually expressed by F. The smaller the spherical radius of the convex lens, the smaller the focal length (marked F, English: focal? The shorter the length). The convex lens can be used for magnifying glasses, glasses worn by presbyopia and hyperopia, cameras, film projectors, microscopes, telescopes, etc.

Lens imaging satisfies the lens imaging formula:?

1/u (object distance)+1/v (image distance) = 1/f (lens focal length)?

(About symbols: when the object is real-time, 1/u is positive, when the object is virtual, 1/u is negative. Similarly, 1/v is a positive sign when the image is a real image, and 1/v is a negative sign when the image is a virtual image).

The difference between convex lens and concave lens;

1。 Touch method (concave lens in the middle thin edge and convex lens in the middle thick edge)

2。 Focusing method (incident parallel light, convergent convex lens, divergent concave lens)

3。 Look with your eyes (put the lens under the words to see if the words are enlarged or reduced after taking pictures)

[Edit this paragraph] Convex lens imaging

When an object is out of focus, it becomes an inverted real image on the other side of the convex lens. There are three kinds of real images: reduction, equal division and enlargement. The smaller the object distance, the larger the image distance and the larger the real image. The object is placed in focus and becomes an upright magnified virtual image on the same side of the convex lens. The greater the object distance, the greater the image distance and the greater the virtual image. ?

In optics, an image gathered by actual light, called a real image, can be accepted by the light curtain; On the contrary, it is called a virtual image, which can only be felt with the eyes. Experienced physics teachers, when talking about the difference between real images and virtual images, often mention such a distinction method: "The real images are upside down, and the virtual images are upright." The so-called "positive" and "negative" are of course relative to the original. ?

The three virtual images formed by plane mirror, convex mirror and concave lens are all positive; The real image formed by concave mirror and convex lens, and the real image formed by pinhole imaging are all inverted without exception. Of course, concave mirror and convex lens can also become virtual images, and the two virtual images they form are also upright. ?

So is the image of the human eye a real image or a virtual image? We know that the structure of the human eye is equivalent to a convex lens, so the image formed by external objects on the retina must be a real image. According to the above rule of thumb, it seems that the object image on the retina should be inverted. But anything we usually see is obviously upright. This problem, which conflicts with the rule of experience, actually involves the regulation of cerebral cortex and the influence of life experience. ?

When the distance between the object and the convex lens is greater than the focal length of the lens, the object becomes an inverted image. When an object approaches the lens from a distance, the image becomes larger and the distance from the image to the lens becomes larger. When the distance between the object and the lens is less than the focal length, the object becomes an enlarged image. This image is not the convergence point of the actual refracted light, but the intersection point of their opposite extension lines, which can not be received by the light screen and is a virtual image. It can be compared to a virtual image formed by a flat mirror (the light curtain can't receive it and can only see it with the eyes). ?

When the distance between the object and the lens is greater than the focal length, the object becomes an inverted image. This image is formed by the light from the candle converging on the convex lens, which is the convergence point of the actual light and can be accepted by the light curtain. This is a real image. When the distance between the object and the lens is less than the focal length, the object becomes an upright virtual image. ?

What is the difference between a convex lens and a convex lens?

1. Different structures?

A convex lens is composed of a transparent mirror whose two sides are ground into spheres?

Concave mirror consists of a concave surface and an opaque mirror on the other side.

2. Different effects on light?

Convex lenses mainly focus light?

Concave mirror mainly radiates light?

3. Different imaging properties?

Is the convex lens refractive imaging?

Is concave mirror a convex lens for reflection imaging or refraction imaging? What can this be like? Positive and negative; Virtual and real; Expansion and contraction. Play the role of spotlight?

Concave mirror is reflective imaging? It can only be a miniature upright image. A lens (including a convex lens) that plays the role of astigmatism is an instrument that transmits light and forms an image by folding it. Light respects the law of refraction. Mirror (including convex mirror) is an instrument that does not transmit light, but reflects back the image, and light obeys the law of reflection. ?

The convex lens can be an inverted enlarged, equal-sized and reduced real image, or an upright enlarged virtual image. Parallel light can converge on the focal point, and the light emitted from the focal point can also be refracted into parallel light. The convex mirror can only form a vertical and reduced virtual image, which is mainly used to expand the field of vision.

(1) times the focal length, inverted to reduce the real image; ?

Double focal length to double focal length, inverted to enlarge the real image; ?

Enlarge the virtual image of the vertical position within a focal length; ?

The real image and the image are on different sides of the convex lens, and the virtual image is on the same side of the convex lens.

(2)

Double focal length, divided into virtual and real?

Twice the focal length. What is the size?

Convex lens imaging rule table

The distance from the object to the lens u? What is the size of the image? Like upside down? Like the actual situation? The distance from the image to the lens v? Application example?

u & gt2f，？ Shrinkage? Handstand? Real image? 2f & gtv & gtf？ camera

u=2f，？ Equal size? Handstand? Real image? v=2f？

2f & gtu & gtf？ Magnified handstand? Real image? v & gt2f？ Projector, slide projector, projector

u=f？ Nothing? Nothing? Nothing? Parallel light source: searchlight

u & ltf？ Enlarge Li Zheng? Virtual image? Nothing? Is the virtual image on the same side of the object? amplifier

(3) Convex lens imaging also satisfies1/v+1/u =1/f.

Using the special light of the lens as the imaging optical path of the lens;

(1), the object exceeds the focal length by 2 times.

(2) The object is between 2 times focal length and 1 times focal length.

(3) The object is in focus.

(4), concave lens imaging optical path

The experimental study on the imaging law of convex lens is as follows: when the object distance is within a focal length, an upright and enlarged virtual image is obtained; When the focal length is between 1-2 times, the inverted magnified real image is obtained; Beyond the double focal length, the real image is reversed and reduced. ?

This experiment is to study and confirm this law. In the experiment, there are the following tables:

Things? Distance? u？ The nature of the image? Where is the image?

Upright or handstand? Enlarge or reduce the virtual image or the real image? What is the image distance v between the same side and the opposite side of the object?

u & gt2f？ Reverse reduction? The real image is different? f & ltv & lt2f？

u=2f？ Inverted size? The real image is different? v=2f？ At this time, the distance between the object and the image is the smallest, that is, 4 times the focal length.

f & ltu & lt2f？ Reverse amplification? The real image is different? v & gt2f？

u=f？ No imaging, because v= infinity (parallel, so infinity).

u & ltf？ Li Zheng? Enlarge the virtual image? Same side? U, v?

This is a table to prove this rule. In fact, lens imaging satisfies the lens imaging formula:?

1/u (object distance)+1/v (image distance) = 1/f (lens focal length)

The camera adopts the imaging law of convex lens.

The lens is a convex lens, the scene to be shot is an object, and the film is a screen.

The light shining on the object is diffusely reflected and imaged on the final film through the convex lens.

When the film is coated with photosensitive substances, chemical changes will occur after exposure, and the image of the object will be recorded on the film.

As for the relationship between object distance and image distance, it is exactly the same as the imaging law of convex lens.

When the object approaches, the image gets farther and bigger, and finally becomes a virtual image on the same side.

In addition, when the object is at infinity, it can be approximately considered that the image is in focus. (Because of this, there is no need to focus the camera. )

The object is far from the convex lens, and the image is far from the convex lens. Where things go, images go.

When an object moves from infinity to the 2F image, it moves faster than the image.