The Imaging Rules of Convex Lenses Yale in China Teachers! ）

When the object distance is less than one time the focal length, it becomes an amplified and upright virtual image.

It is not as good as a double focal length.

When the focal length is greater than 1x and less than 2x the focal length, it becomes an inverted cube-sized real image, and when the elephant is equal to 2x the focal length other than 2 times, it becomes an elephant of equal size.

When the focal length is greater than 2x, it becomes an inverted and reduced reality, and the image is between 1x and 2x the focal length. Fig.

The representation in the picture is relatively clear, you can go and see it.

Memorize mantras.

1) One time the focal length is divided into virtual and real, two times the focal length is divided into size, twice the focus of the object image, etc.

The real image is always reversed. The near image of the object becomes larger, and the distant image of the object becomes smaller.

The virtual image is always on the same side. The far image of the object becomes larger, and the near image of the object becomes smaller.

The size of the image is fixed, the distance between the object and the distance from the image is changing.

2) One double focal length is divided into virtual and real, and two times the focal length is divided into size. The near image of the object becomes larger, and the distant image of the object becomes smaller.

Note: The double focal length referred to here is the distance from the point where the parallel light source converges to the main optical axis through the lens to the optical center of the lens, which can also be directly called the focal length; A double focal length is twice that distance.

[Convex lens imaging law oral decision memory method].

One focal is divided into virtual and real, and two focal points are divided into size; The virtual image is on the same side, and the distant image of the object becomes larger; The real image is reversed, and the distant image of the object becomes smaller".

Additional experimental rules.

1. Lenses and classification.

Lens: Made of transparent material (usually glass) with at least one surface that is part of a spherical surface and a lens that is much thicker than its spherical radius.

Category: Convex lenses: Thin edges, **thick.

Concave lens: Thick edges, **thin.

2. Main optical axis, optical center, focus, focal length.

Main optical axis: A straight line through two spheres.

Optical center: There is a special point on the main optical axis, through which the direction of light propagation does not change. Focus: The point at which the convex lens can make the rays parallel to the principal axis converge on the main optical axis, which is called the focal point of the lens, which is represented by "f".

Imaginary focus: The rays parallel to the main optical axis become divergent after passing through the concave lens, and the reverse extension line of the divergent rays intersects at one point on the main optical axis, which is not the convergence point of the actual rays, so it is called virtual focus.

Focal length: The distance from the focal point to the center of light is called the focal length, which is represented by "f".

Each lens has two focal points, focal lengths, and a center of light.

3. The effect of the lens on light.

Convex lens: Acts as a converging light element.

Concave lens: Divergent to light.

4. Convex lens imaging rules.

Object distance (u) Imaging size Virtual and real image position Image distance (v) Application.

U > 2f zoomed out real image on both sides of the lens f < v <2f camera.

u = 2f equal to the size of the real image on both sides of the lens v = 2f

f < u < 2f magnification real image both sides of the lens v > 2f slide projector.

u = f is not formed.

u < f magnification virtual image ipsilateral to the lens v > u magnifying glass.

The imaging law of convex lens is one of the compulsory test points in the high school entrance examination.

The lecture is very perfect, the lesson of convex lens is one of the difficulties in junior high school, and students must master it well.

Natural science cannot be learned with formulas, this is done by the right brain, fully stimulate your imagination, use images to think, to feel, and repeatedly verify and think in practice, you can truly understand and master their laws. But then again, it is true that a small number of people imagine that these are a little difficult, just like some boys can't remember words even if they are killed!

The near image of the object becomes larger, and the distant image of the object becomes smaller.

Object distance (u) Nature of the image Image distance (v) Position relationship of the image.

u > 2f handstand, shrink, real image fu = 2f handstand, equal size, real image v = 2f image size turning point, image opposite.

f< u<2f handstand, magnification, real image v > 2f image opposite.

u = f does not image the virtual reality of the image, upright inverted, the image is on the same side and the opposite side of the turning point.

u < f upright, magnified, virtual v > u ipsilateral to the image.

The above situation is represented on an optical path diagram for easy understanding, see the figure below

The imaging law of convex lens is one of the compulsory test points in the high school entrance examination.

Convex lens imaging law: a law of optics.

Object distance The nature of imaging Applied image distance Forward inverted size change Virtual and real situation.

u>2f 2f>v>f handstand shrink real camera 2f>u>f v>2f handstand zoom in real slide projector u memory formula: one focal point is divided into virtual and real, two focal points are divided into size, the near image of the object is increased by the far image, the real is inverted on the opposite side, and the virtual is on the same side.

A bunch of dog-eating words, the principle that.

Here's a table:

The nature of the object distance u image, the position of the image is upright or upside down, magnifying or shrinking, the virtual image or real image is on the same side and opposite side of the object, and the image distance is v

U>2F inverted handstand scales out real image heteroside F2F

u=f－－－

Convex lens imaging can be boiled down to the following five situations:

Rule 1: When the object distance is greater than 2x the focal length, the image distance is between 1x the focal length and 2x the focal length, and it becomes an inverted and reduced real image. At this time, the image distance is smaller than the object distance, the image is smaller than the object, and the object image is on the opposite side. Applications: Cameras, camcorders.

Rule 2: When the object distance is equal to 2 times the focal length, the image distance is also 2 times the focal length, forming an inverted and equal-sized real image. At this time, the object distance is equal to the image distance, the image and the object are equal in size, and the object is on the opposite side.

Rule 3: When the object distance is less than 2 times the focal length and greater than 1 times the focal length, the image distance is greater than 2 times the focal length, and it becomes an inverted and magnified real image. At this time, the image distance is greater than the object distance, the image is larger than the object, and the object image is opposite. Applications: projectors, slide projectors, movie projectors.

Rule 4: When the object distance is equal to 1 times the focal length, it will not be imaged, and it will be emitted as parallel light.

Rule 5: When the object distance is less than 1 times the focal length, it becomes an upright and magnified virtual image. At this time, the image distance is greater than the object distance, the image is larger than the object, and the object image is on the same side. Application: Magnifier.

One is divided into virtual and real, and two times is divided into size.

It means that something greater than twice the focal length is like a real image, and something less than twice the focal length is a virtual image.

The real image is always upside down, and the virtual image is always upright.

The real image is on the other side of the convex lens, and the virtual image is on the same side of the convex lens.

For example, 2f >something" f asks imaging.

f, the real image, the real image is upside down. <2f, zoom in. The answer is: handstand, magnified reality.

The rest is the same.

This is very easy to remember, the double focal length and the double focal length are the dividing points, the image distance and the object distance must be between the first and the second focal length, and the other is outside the double focal length, for example, if the image distance is outside the double focal length, the object distance is between the first and the second focal length; Conversely, if the image distance is between one and two focal lengths, the object distance is outside the two focal lengths.

These two situations become an inverted reality. It's easy to understand by drawing a light path diagram by yourself. Drawing a light path diagram is the easiest to understand and memorize. All you need to do is draw two typical rays of light, i.e. two lines that pass through the center of the lens and parallel to the optical axis.

Distance from object to lens u size of image positive and inverted image virtual real distance from image to lens v application examples.

u is the object distance, v is the image distance, and f is the focal length.

u>2f, inverted reduced real image 2f>v>f camera u=2f, inverted equal size real image v=2f

2f>u>f Inverted magnified real image v>2f Projector, slide projector, projector u=f No imaging Directional light source: Searchlight.

u< fUpright magnified virtual image None virtual image on the same side of the object Magnifying glass.

U>2F inverted handstand scales out real image heteroside F2F

u=f －－

u

u is the object distance, v is the image distance, u2f is reduced, and real f

U>2F, zoom out of the inverted real image camera.

u=2f, equal to the large inverted real image of the slide.

2ff, zoom in on the inverted real image projector.

u = f is not formed.

u f, magnify the upright virtual image of the telescope.

2F is divided into size, and 1F is divided into real and virtual.

Camera, inverted, zoomed out, real image.

Projector, handstand, magnification, real image.

Magnifying glass, upright, magnifying virtual image.

Focal length, handstand, and other large real images.

The object and the image it forms are separated from each other on either side of the convex lens, e.g., the object is on the left side of the convex lens, the image is on the right side of the convex lens, the object image moves to the left (away from the convex lens), and the image moves in the same direction - to the left (near the convex lens).

In addition, you want to know the laws of imaging, and I will introduce you to a method:

Draw a diagram of the convex lens imaging on a piece of paper (i.e., place the luminous object at a place greater than 2 times the focal length, equal to the 2nd focal length, less than 2 times the focal length and greater than 1 focal length, 1 time focal length, less than 1 focal length, and less than 1 focal length, and then draw the position of the image it makes).

You have to draw this diagram several times until you know that you are proficient in drawing, so that when you do the problem, this diagram will appear in your mind, and the problem will be made naturally.

Now, do you know why?

This section is very important, learn it well, it will be of great help to future learning, oh yes, no, you can continue to ask me.

Object distance (u) Nature of imaging Image position Image distance (v) Application.

U > 2F Handstand Zoom Out Real Image Both sides of the lens F < V <2F camera.

u = 2f handstand equal to large real image on both sides of the lens v = 2f

f < u <2f handstand magnification real image both sides of the lens v > 2f slide projector.

u = f is not formed.

u < f upright magnifying virtual image ipsilateral to the lens v > u magnifying glass.

[Convex lens imaging law oral decision memory method].

Oral decision one: one focal is divided into virtual and real, and two focal points are divided into size; The virtual image is positive on the same side; The real image is reversed, and the distant image of the object becomes smaller".

Oral decision 2: convex lens, great ability, photography, slide and magnification; The outside of the double coke is small, and the inside of the double focus is large;

If the object is placed in the focus, the image is large on the same side; A rule is kept in mind, and the near and far images of things become larger.

Note: When drawing, the focal length of both sides must be equal, F is one time focal length, P is two times the focal length; Lenses can be drawn simply as straight lines.

The imaging law of convex lens is one of the compulsory test points in the high school entrance examination.

Rule: When the object distance is greater than 2 times the focal length, it becomes an inverted and reduced real image;

When the object distance is equal to 2 times the focal length, it becomes an inverted and equal-sized real image;

When the object distance is between 1x and 2x the focal length, it becomes an inverted and magnified real image;

When the object distance is equal to 1x the focal length, the image is not imaging;

When the object distance is less than 1 times the focal length, it becomes an upright and magnified real image.

Formula: 1 U+1 V=1 F, i.e., the sum of the reciprocal of the object distance and the reciprocal of the image distance is equal to the reciprocal of the focal length.

The imaging law of convex lens is shown in the figure as follows:

I hope it helps you, and if you have any questions, you can ask them

a.The image is always upright.

b.If it looks like it's upright, it will gradually enlarge.

c.When the lens is far away from the book, you will see an inverted magnified image dIf you reach a certain position, you won't see any image, then that point is the double focal length point of the lens, why choose b, isn't it that the object distance becomes larger, the image distance becomes smaller, and the image becomes smaller?

Ask for a reason, do not copy and paste!! Explain in detail!