Physical lens imaging, imaging rules and applications of lenses

When the object is placed outside the focal point, it becomes an inverted real image on the other side of the convex lens, and there are three types of real images: reduced, equal size, and magnified. The smaller the object distance, the larger the image distance, and the larger the real image. The object is placed in focus, and the virtual image is magnified upright on the same side of the convex lens.

The smaller the object distance, the smaller the image distance, and the smaller the virtual image.

When a convex lens is placed on the ground in sunlight to form the brightest and smallest spot, the distance from the ground to the lens is the focal length of the lens. What can be connected with the light screen is the real image, such as the hand shadow, when the convex lens light source is placed outside the focus, the light screen can be used on the other side of the lens to undertake, that is, there is an image on the light screen, this is the real image, can not be undertaken with the light screen, such as plane mirror imaging, there is no image on the other side of the plane mirror, such an image is a virtual image.

The first is the convex lens.

1.The most important function of a convex lens is to concentrate light.

2.Three special rays that must be mastered to learn convex lenses (there is a picture below) 3Features of convex lens imaging:

u is the object distance. v is the image distance.

f is the focal length u>2f, zoomed out.

Handstand. Real.

2f>v>f

Camera u=2f, equal size.

Handstand. Real.

v=2f2f>u>f

Magnify. Handstand.

Real. v>2f

Projectors, slide projectors, projectors.

U=F is not imaged.

Directional light source: Searchlight.

The virtual image is on the same side of the object.

Magnifying glass. Then there are the concave lenses.

1.Concave lenses have a divergent effect on light.

2.The concave lens looks like an upright and shrunken virtual image.

The first question is that if the object is inverted and magnified at a distance of 40 cm from the lens, if it can be a real image, then 40 cm must be larger than the focal length, and if it is an enlarged image, it must be less than 2 times the focal length. This is the slide projector principle. Please refer to the physics textbook for the second year of junior high school.

Question 2. Because it is an inverted magnified image, the focal length of the convex lens should be less than 12 and greater than 6

Therefore, when the distance is 8, it is still an inverted magnified image.

According to the law of imaging, when the image is magnified inverted, the object distance is greater than 1x and the focal length is less than 2x the focal length, so B is selected for question 1

Question 2: Because it is an inverted magnified image, the focal length of the convex lens should be less than 12 and greater than 6

Therefore, when the distance is 8, it is still an inverted magnified image.

2f>40>f is based on the principle of convex lens imaging2It's supposed to magnify the real image, after all, it's a concave lens.

The imaging rules and applications of lenses are as follows:

Imaging law: Once the object is placed outside the focus, it becomes an inverted real image on the other side of the convex lens, and the real image is reduced, equal and magnified. The smaller the object distance, the larger the image distance, and the larger the real image.

The object is placed in focus, and the virtual image is magnified upright on the same side of the convex lens. The larger the object distance, the larger the image distance, and the larger the virtual image, as shown in the figure below

Principle application: lens. The lens is a convex lens, the scene to be illuminated is the object, the film is the screen, the light shining on the object is diffusely reflected through the convex lens to make the image of the object on the final film, the film is coated with a layer of light-sensitive substance, it undergoes chemical changes after **, and the image of the object is recorded on the film.

Lenses are made according to the law of refraction of light and are divided into convex lenses and concave lenses. Lenses can be widely used in security, automotive, digital cameras, lasers, optical instruments and other fields, with the continuous development of the market, lens technology is more and more widely used. Here's an example::

The camera is made using the principle that a convex lens can be used to reduce the inverted real image. The lens of the camera uses a convex lens or lens group, and the light from the object passes through the camera lens to form an inverted, shrinking real image on the film, the farther the object is from the lens, the smaller the image is formed, and vice versa. The film is coated with a layer of photosensitive substance, which undergoes chemical changes after the late skin**, and the image of the object is recorded on the film, which becomes a negative after development and fixing, and then uses the negative to develop and print to obtain a photo.

Lenses are divided into concave lenses and convex lenses, which are mainly made of glass or lead glass (lead glass has a large refractive index), using light obliquely on the surface of transparent objects, using the difference in the refractive index of two transparent objects, so that the light can be refracted into different images, that is, the refraction principle of light. The specific image is determined by the relationship between convex or concave lenses, as well as object distance and focal length. What is the relationship between object distance, image distance, and focal length?

1 U+1 V=1 F (U is the object distance, V is the image distance (negative number is the virtual image), F is the focal length (negative number is the concave lens)), the concave lens can only be reduced into a reduced virtual image, and the convex lens can be reduced or magnified into a real image and a magnified virtual image according to the object distance and focal length

1) Convex lens imaging rules:

1. **Description:

2. Diagram description:

2) Concave lens imaging rules:

1. Language description: It can only generate upright and shrunken virtual images.

2. Legend description:

Therefore, whether it is a convex lens or a concave lens, the imaging principle is to use the different refractive indices of different transparent media, the light rays are emitted from one medium into another medium, the angle of incidence and the angle of refraction are not equal, so as to produce different images, and their common point is: they all conform to the imaging formula of 1 U+1 V=1 F (U is the object distance, V is the image distance (negative number is a virtual image).

Lenses are divided into convex lenses and concave lenses.

Convex transparency: Put the object out of focus, on the other side of the convex lens into an inverted real image, the real image has three types: reduced, equal size, and magnified.

The smaller the object distance, the larger the image distance, and the larger the real image. 】

The object is placed in focus, and the virtual image is magnified upright on the same side of the convex lens.

The larger the object distance, the larger the image distance, and the larger the virtual image. 】

The concave lens has a divergent effect on light, and its imaging rules are much more complex.

The principle of refraction and propagation of light along a straight line is utilized by a lens imaging device. The simple device is to use a sealed carton. Drill a small hole in the middle of the front of the carton.

Then attach a well-sized flat lens to the back of the carton. The lens surface should be aligned with the small hole as much as possible. Place some items (such as candles) in front of the small hole when using

The image of the object is upside down through a small hole and imaged upside down on the lens.

Eighth-grade physics convex lens imaging rules.

A lens is an optical element made of a transparent substance (such as glass, crystal, etc.) that affects the wavefront curvature of light. It is a device that can aggregate or disperse light, and the resulting image has both real and virtual images. It is widely used in various fields such as security, car wear, digital camera, laser, optical instrument and so on.

A variety of ordinary colorless optical glass, including fused silica, calcium fluoride, magnesium fluoride, silicon, germanium, zinc selenide and other materials; As well as plano-convex lenses, biconvex lenses, plano-concave lenses, biconcave lenses, super-hemispherical lenses, small ball lenses, meniscus lenses, cylindrical lenses, rod lenses, glued lenses, etc.

Imaging rules of lenses and convex lenses.

1.The lens is represented by a lens symbol (there are two V-shaped signs at both ends of a line segment), the main optical axis is drawn, and the optical center and focus are marked to obtain the characteristics of the image formed by the lens (such as virtual and real, size, forward and backward, etc.) according to the intersection point of two of the three special rays of the lens (generally the light that has been used as the center of light and the light parallel to the main optical axis is better).

2.When imaging with a lens, all the light rays emitted by each point on the object that shine on the lens are imaged in the same position, blocking a part of it, and not affecting the imaging of other rays emitted to the lens, so the complete image can still be seen, but because the light on the image is reduced, the brightness of the image on the screen will be dimmed.

3.Convex lens imaging rules:

1) One of the conditions that need to be met for the convex lens to form a real image is; (2) Conjugate imaging means that the size of object distance and image distance can be interchanged, and in the two cases, they are respectively enlarged and reduced.

4.When looking at a clock outside of the double focal length through a convex lens, the image of the second hand still rotates clockwise, because it is an inverted real image at this time, and it is still in the normal direction when viewed backwards, so it still rotates clockwise.

The law of convex lens imaging is an optical law. In optics, the image that is formed by the convergence of actual light rays and can be presented on the optical screen is called a real image; An image that is formed by the convergence of the reverse extension lines of light rays and cannot be displayed on the light screen is called a virtual image. When talking about the difference between real and virtual images, such a method is often mentioned:

The real image is upside down, while the virtual image is upright. ”

In the case of thick meniscus concave lenses, the situation is more complicated. When the thickness is large enough, it is equivalent to a Galilean telescope, and when it is thicker, it is equivalent to a positive lens.

Its imaging principle is: the object is placed outside the focus, and the other side of the convex lens becomes an inverted real image, and the real image has three types: reduction, equal size, and magnification. The smaller the object distance, the larger the image distance, and the larger the real image.

At 2x focal length, it will be an inverted real image. The object is placed in focus, and the virtual image is magnified upright on the same side of the convex lens. The larger the object distance, the larger the image distance, and the larger the virtual image.

No imaging is done in focus. In optics, the image formed by the convergence of actual light is called a real image, which can be undertaken by an optical screen; Otherwise, it is called an illusion and can only be perceived by the eyes. In contrast to the original object, the real image is inverted, while the virtual image is upright.

Transmission electron microscope is a high-resolution, high-magnification electron-optical instrument that uses an electron beam with a very short wavelength as the illumination source and focuses the imaging with an electromagnetic lens. Transmission electron microscopy projects an accelerated and concentrated beam of electrons onto a very thin sample (sheet< 100 nm, particle < 2 um), and the electrons collide with the atoms in the sample and change direction, resulting in solid angle scattering. **The difference in light and dark (black, white and gray) is related to the atomic number, electron density, thickness and other aspects of the sample.

The imaging method is similar to that of the Lingcong optical microscope, except that electrons are used instead of photons, electromagnetic lenses are used instead of glass lenses, and the magnified electron images are displayed on the phosphor screen.

Transmission electron microscopy is classified according to the accelerating voltage, which can usually be divided into conventional electron microscopy (100kV), high-voltage electron microscope (300kV) and ultra-high-voltage electron microscope (above 500kV). Increasing the acceleration voltage can increase the energy of the incident electrons, which is conducive to improving the delay resolution of the electron microscope. At the same time, it can improve the ability to penetrate the specimen.