Find a complete review material for junior high school physics convex lens.

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

It is determined by a variety of factors, mainly object distance, image distance and focal point When the object is far away from the lens, the real image is routinely reduced; When the image is closer to the lens, the object is closer to the lens; When the object is closer to the lens, it becomes an example of a magnified real image, and the image is farther away from the lens; When the object is very close to the lens, it becomes an upright magnified virtual image, and the image is on the same side.

Added: When U 2F, it becomes an inverted and reduced real image, and when U=2F, it becomes an inverted real image of the same size, and the opposite side of the image is V=2F;

When f u 2f, it becomes an inverted magnified real image, and the image is on the opposite side v 2f;

When u=f, no imaging is performed.

When u f, it becomes an upright magnified virtual image, and the image is on the same side v u;

u= object distance v=image distance f=focal length.

The knowledge points of physical convex lens imaging in junior high school are as follows:

1. Rule 1: When the object distance is greater than 2 times the focal length and high land distance, the image distance is between 1 times the focal length and 2 times 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.

2. 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 size 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.

3. 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 image is located on the opposite side of the object. Applications: projectors, slide projectors, movie projectors.

4. 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.

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

6. 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.

7. Oral decision two: things are far away and real like small and near, and things are close and real like big and far. If the object is placed in the focus, it will be upright to magnify the virtual image. The slide is like a big one, and the object is between one and two focuses. The camera is not small, and the object is twice as far as the focal length.

1. Lens. 1. Convex lens: the thickness of the middle is greater than that of the edge.

2. Concave lens: the thickness of the middle is less than that of the edge.

Second, the role. 1. The convex lens has a converging effect on light.

2. The concave lens has a divergent effect on light.

Three、......Primary optical axis.

F Optical Center f

Optical center: The direction of light propagation through the optical center remains unchanged.

Focus: fFocal length: Focus to the center of light.

Fourth, drawing. 1. The light rays parallel to the main optical axis pass through the focal point on the other side of the lens.

2. The light rays that pass through one side of the focal point pass through the convex lens and are parallel to the main optical axis on the other side.

3. The direction of the light through the center of light remains unchanged.

V. Conclusions. Object Distance Imaging Distance Characteristics of Image.

l Matter 2f f

The title says that point S emits light to point n on the convex lens, and the refracted light intersects at point A on the right side of the convex lens, indicating that S is outside the focal point and point A is the real image point.

The refracted rays from the light emitted from the S point (outside the focal point) to any point on the convex lens intersect at point A.

Because. The object point S, the optical center O, and the image point A are on the same line.

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

1) Outside the double focal length, inverted to reduce the real image; The double focal length here refers to the distance from the point where the collimating light source converges through the lens to the center of the lens, and the double focal length refers to the place where it is twice as far

1x focal length to 2x focal length, inverted magnification of real image;

Within one time of the focal length, the virtual image is magnified upright;

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

The object distance is the distance from the object to the mirror.

Focal length is the distance from the focal point to the mirror.

F2F into a handstand.

Zoom in on the real image. u=2f

into a handstand and so on.

Real image u>2f

F into a handstand shrinks.

The real image is upright and magnified.

Virtual image u=f does not image f

Indicates the focal length of the lens.

u denotes the distance between the object and the lens (referred to as object distance).

1. The distance from the object to the lens is called the object distance, the distance from the focus to the lens is called the focal length, and the focus is the point that gathers after refraction. 2、

When the focal length of 2x is greater than the object distance and 1x the focal length, it will be enlarged upside down. 3. When the object distance is equal to 2 times the focal length, it will be inverted and equal in size. 4、

When the focal length is less than the object distance, the handstand is reduced. 5、

When the focal length of 1x is greater than the object distance, it will be magnified upright and will not be imaged. 6 without this.

Objects within 1x focal length are virtual images and will not be imaged.

Objects are real outside of 1x focal length.

1.The convex lens, candle flame, and light screen are not in a straight line; If the real image of the candle flame is on the upper part of the light screen, then adjust the light screen to (up), and if the real image of the candle flame is lower than the light screen, then adjust the light screen to (down).

cm, inverted, magnified, real image, convex lens into inverted, equal size of the real image condition is u=2f, that is, the object distance is equal to 2 times the focal length, 15cm=2f, then f=; U=2F, then V=U=2F=15cm; If the candle is moved closer to the lens by 5cm, the object distance is 10cm, f

1.When using a camera to move from a close-up to a long shot, the purpose of retracting the lens is to reduce the distance between the lens and the film (i.e., image distance);

2.Theoretically, the object distance can be reduced, so as to increase the image distance, but there is no such long lens that can be stretched, for example: 1 meter long lens, how to store and carry

3.When the lens is retracted, the image distance becomes smaller. This is because when shooting long shots, the object distance increases, and the image distance decreases.

1 pair, the object distance increases, and the image distance must be reduced.

Look at this formula: 1 U + 1 V = 1 fu is the object distance, v is the image distance, and f is the focal length.

As long as the above equation is met, imaging is inevitable.

As camera f does not change, it is obvious how to change one of you or v and the other.

This problem is nonsense, and the moving light screen can't see a clear image, just one reason: the position of the convex lens is wrong

If you insist on saying three, then you write:

1. The convex lens is too close, and the candle is within one double the focal length, which is a virtual image 2, the convex lens is too close, and the candle becomes a real image in a place other than the desktop, resulting in the inability to focus within the desktop 3, the convex lens is too far, and the candle is imaged very close to the convex lens, and the light screen cannot reach 4, the candle, the light and the convex lens are not strictly arranged in the same straight line (different axes)5, and the convex lens is not placed vertically along the optical axis.

6. The light screen is not placed vertically along the optical axis.

7. The candle flame is unstable.

Look at the writing, in short, it's all kinds of wrong positions.

The candle is too far away.

The candle is in focus.