Why do convex and concave lenses change the direction of light propagation?

To put it simply, light can only travel in a straight line, and of course it travels through a medium. You look at the plane mirror, both sides of the mirror are flat, that is, when the light passes through it, because every particle of the plane is the same, smooth. Therefore, if the medium does not change, the light will naturally remain the same.

And the medium means to spread with the help of something. For example, vehicles such as automobiles and airplanes must follow the direction of the road when driving on winding roads. As soon as the road turns, the car has to follow the turn, otherwise you know the consequences.

Then when the light encounters the convex and concave lens, because the medium changes, it also has to change the direction, the light changes direction is refraction, and the refraction is like a ball, such as a billiards, if it touches the case, it will be **, and the rolling direction will also change. But it's still a straight path, and the light is the same, it is refracted but the direction changes and it still travels in a straight line. But in which direction it spreads.

It depends on which direction the convex and concave lens refracts it. The principle of the direction of refraction follows a rule of right angles. There is a refractive index in the formula, and the refractive index is determined by the medium.

The direction in which the refraction is carried out is determined by the angle of refraction. The angle of refraction is in turn determined by the refractive index. I can't be firm with you anymore.

There are too many, and there are formulas involved. If you understand light as a car, and two lenses as a winding road, it is easy to understand.

The phenomenon of refraction of light from the photophobic medium to the optically dense medium occurs and the air is the photophobic medium relative to the glass.

When light enters the lens, it is refracted on the first side and refracted again when it exits the lens, causing the light to change direction.

Convex lenses can concentrate light, and concave lenses can diverge light.

When light enters the lens, it is refracted first, and when it exits the lens, it is refracted again, causing the light to change direction.

Refraction occurs through a lens.

The first diagram is a convex lens.

If the incident ray is parallel to the main optical axis, the refracted ray will pass the focus;

The second diagram is a concave lens.

The refractive light shed Kai line is parallel to the main optical axis, then the extension line of the incident beam residual light is over the focus, so the answer chain slag is called:

Yes, flat mirrors, convex lenses, and concave lenses can all change the direction of light propagation, but the direction and angle of the change are different. Flat mirrors change the direction of light propagation by reflection, and convex and concave lenses change the direction of light propagation by refraction.

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 larger the object distance, the greater the distance between the image and the town, and the larger the virtual image. No imaging is done in focus. At 2x focal length, it will form an inverted real image.

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. Experienced physics teachers, when talking about the difference between real and virtual images, often mention such a way to distinguish between real and virtual images: "Real images are inverted, while virtual images are upright."

The so-called "upright" and "inverted" are, of course, relative to disturbing the original object.

The three virtual images formed by plane mirrors, convex mirrors and concave lenses are all upright; The real images made by concave mirrors and convex lenses, as well as the real images made by small hole imaging, are all inverted without exception. Of course, concave mirrors and convex lenses can also be made into virtual images, and the two virtual images they form are also upright.

Three special rays.

1. The propagation direction of the light passing through the center of light does not change after passing through the lens, as shown in the following figure:

2. The light parallel to the main optical axis passes through the focal point after passing through the convex lens; After passing through the concave lens, it diverges outward, but its reverse extension line must pass through the focus (so the convex lens has a converging effect on the light, and the concave lens has a divergent effect on the light) as shown in the following figure:

3. The light rays passing through the focal point of the convex lens are parallel to the main optical axis after passing through the convex lens; The light rays directed at the opposite focus are parallel to the main optical axis after passing through the concave lens; As shown below:

The deflection effect of the lens on the light is due to the deflection of the light through the "prism", that is, because of the refraction of the light by the medium.

When the light passes through the center of the lens, the apex angle of the "prism" at this point is 0, and the angle between the incident ray and the normal is 90 degrees, and the light does not refract, so the propagation direction of the light remains unchanged.

For air, the lens is a light-dense medium, so the light passing through the lens will be deflected to a certain extent, and there will be different degrees of deflection in the horizontal direction due to the different angle of incidence. The surface of the lens has a certain curvature, so the angle of incidence of light is different. (The surface is normal perpendicular to the tangent of the incident point.)

Under such influence, the parallel light will converge (diverge) through a convex (concave) lens. If the angle of the lens is reduced so that it tends to be flat glass, the degree of convergence (divergence) decreases.

The reason why the direction of propagation of light through the center of light does not change.

In fact, a beam of light will be refracted on the first surface before it reaches the center of the convex lens, and then after passing through the lens, passing through the center of light, and going out of the second surface, another refraction will occur, because the two sides are exactly stacked with respect to the center of light, so the two refractions happen to make the outgoing ray parallel to the original ray (not coincident). However, for the sake of convenience, when we are studying, for the sake of convenience, we regard the lens as a lens whose thickness is not remembered (we will learn the lens whose thickness cannot be ignored later), so that the direction of passing light remains unchanged and is still a straight line. I hope to adopt.

The direction of light propagation through the center of light does not change.

2) The light rays parallel to the main optical axis are refracted and overfocused.

3) The light rays that have passed through the focal point are refracted and parallel to the main optical axis.

The direction of light propagation through the center of light does not change in the concave lens (1).

2) The reverse extension line of the ray refracted by the ray parallel to the main optical axis crosses the virtual focus, and (3) the ray rays directed at the virtual focus are refracted and parallel to the main optical axis.

Resources.

Because the light passing through the center of light is perpendicular to the surface of the lens. The angle of incidence is 0 degrees, so the direction does not change.

There is a refraction in it, a refraction in the center of light, a refraction on both sides, and a parallel light.