How to do the experiment of the law of convex lens into magnifying real images .

If the focal length of the convex lens is 10cm) position from left to right:

The candle is about 20cm away (e.g. U 25cm or larger); , convex lens at (middle) 50 cm; The light screen within 20cm (such as V 18cm) can be bright, clear, magnified real image.

Experimental equipment: a set of light holder (with accessories), a convex lens, a candle, a match box (or a lighter), and a dirt tank.

Experimental Procedure. Operational procedures and records.

1 Check the equipment.

Check whether the equipment required for the experiment is complete;

Observe and record that the minimum index value of the coordinate scale of the optical apparatus is correct (1 point).

1 point. 2. Assemble the experimental setup.

The convex lens, candles, and light screens are correctly placed on the light base (1 point);

The position of the convex lens on the optical apparatus base is recorded and the scale value is correct (1 point);

Adjust the height of the convex lens and light screen so that the center is about the same height as the candle wick (1 point).

3 points. 3 Complete the experiment.

Accurately and quickly get a bright, clear magnified real image of the candle on the light screen.

At this time, the ruler scale and object distance of the position of the candle on the light holder are correct.

At this time, the ruler scale and image distance of the position of the optical screen on the optical device base are correct.

It is concluded that the imaging law of the convex lens into a magnified real image is correct.

**The introduction of the convex lens imaging law experiment is as follows:

Procedure: Record the focal length of the convex lens. Place candles, convex lenses, and light screens from left to right on the light base, and adjust the height of the convex lens and the light screen so that the center of the convex lens and the light screen is about the same height as the center of the candle flame. (Make the image into the light screen**).

Fix the position of the convex lens so that the candle flame is 2f (u>2f) of the convex lens, move the light screen to find the image, and in the process of moving, the eye should pay attention to the imaging on the light screen until the clearest image appears on the light screen.

The situation of the image at this time is an inverted, shrunken real image. Measure and record the object distance and image distance at this time, and then compare the image distance and object distance with the f, 2f of the convex lens (f<>).

Purpose and conclusion of the experiment:

1. Light the candle during the experiment, so that the center of the candle flame, the convex lens, and the light screen is roughly in the same straight line and the same height, and the purpose is to make the image of the candle flame appear on the light screen.

2. Keep the position of the convex lens still, change the distance from the candle to the convex lens, adjust the position of the light screen, make the candle flame a clear image on the light screen, and write down the object distance, image distance and imaging situation under different circumstances; Place the candle in the focal point of the convex lens and look through the lens on the other side to create the image.

3. If during the experiment, no matter how you move the light screen, you can't get the image on the light screen, there may be reasons: the candle flame is in focus; The candle flame is in focus; The center of the candle flame, convex lens, and light screen is not at the same height; The distance between the candle flame and the convex lens is slightly larger than the focal length, and the imaging is far away, and the light screen of the light holder cannot be moved to this position.

The imaging rules of convex lenses are as follows:

1. The object distance is greater than twice the focal length, and the inverted real image is reduced.

2. The object distance is equal to twice the focal length, and it becomes an equal large inverted real image.

3. The object distance is between 1 times the focal length and 2 times the focal length, forming a magnified inverted real image.

4. The object distance is less than 1 times the focal length, and the upright virtual image is magnified on the same side.

5. If the object distance is equal to 1 times the focal length, it cannot be imaged.

The memorization formula of the imaging law is as follows: one time the focal length is divided into virtual and real, and two times the focal length is divided into size. The far image of the object becomes smaller, and the near image of the object becomes larger.

Applications of convex lens imaging

1. Camera.

The lens of a camera is a convex lens, and the distance between the object and the lens (object distance) is greater than 2 times the focal length, forming a zoomed out, inverted real image.

2. Projector.

The lens of the projector is a convex lens, and the distance from the object to the lens (object distance) is greater than 1 times the focal length and less than 2 times the focal length, forming a magnified and inverted real image.

Note: To make the image larger for cameras and projectors, the lens with pants should be close to the object, away from the film and screen.

3. A magnifying glass.

Magnifiers are convex lenses; The distance between the object and the lens is less than 1 times the distance of the focal transport, and it becomes a magnified and upright virtual image.

Note: Make the object larger.

4. Eyes. The lens of the eye is equivalent to a convex lens, and the retina is equivalent to a light screen (film). The hyperopic eye cannot see near objects clearly, and the near objects are imaged behind the retina, so they need to wear a convex lens to adjust.

During the experiment, the object distance and image distance should be measured with a scale

When the object distance is 40cm, and the image distance is 13cm, it becomes an inverted and reduced real image, so 40cm 2F, 2F 13cm F, so 13cm F

The object distance is 24cm, and when the image distance is 17cm, it becomes an inverted and reduced real image, so 24cm 2F, 2F 17cm F, so 12cm F

The object distance is 18cm, and when the image distance is reached, it becomes an inverted and magnified real image, so 2F is 18cm F, so the object distance is 13cm, and when the image distance is 43cm, it becomes an inverted and magnified real image, so 2F 13cm F, 43cm 2F, so 13cm F

Therefore, when the convex lens becomes a real image, the object distance is greater than the image distance, and it becomes an inverted and reduced real image; When the object distance is less than the image distance, it becomes an inverted and magnified real image

So the answer is: scale; d；Less than

Problem solving ideas: (1) To solve this problem, it is necessary to master the placement requirements of each equipment in the convex lens imaging, because to make the convex lens image, the convex lens should be faced with the candle, and the light screen should be faced with the convex lens, so that the image can be made on the light screen

2) In the experiment, in order to make the image in the center of the light screen, the height of the candle flame, the convex lens and the light screen should be adjusted so that their centers are about the same height

3) In physical experiments, in order to make the experimental results more credible and prevent the one-sidedness of the experimental conclusions, it is usually necessary to do it several times

4) To solve this problem, you need to know that the convex lens is an inverted real image If the image of the candle flame is above the light screen, it means that the position of the candle flame is too low, so the candle flame should move up relative to the convex lens

1) In order to make the light of the candle flame pass through the convex lens, the surface of the convex lens should be perpendicular to the candle flame, so the surface should be perpendicular to the orbit of the light fixture base, and at the same time, in order to make the image on the light screen, the surface of the light screen should be perpendicular to the orbit of the light frame

2) In the process of doing the experiment, adjust the height of the convex lens and the light screen so that the center of the candle flame, the convex lens and the light screen are about the same height, so that the image of the candle flame is in the center of the light screen

3) Xiao Ming did three experiments when the object distance was between one and two times the focal length of the convex lens imaging, so as to make the experimental conclusions more credible and eliminate the one-sidedness of the experimental conclusions

4) Since the convex lens is an inverted real image, the candle is too short so that the image is above the center of the light screen, so the candle should be adjusted upwards or downwards

Because the height of the candle flame is reduced and the light screen is not adjusted, after adjusting the position of the convex lens, when the center of the candle flame and the convex lens and the center of the light screen are in a straight line, the candle flame is below the main optical axis of the convex lens

So the answer is: (1) vertical; (2) the same height; (3) makes the conclusion general; (4) down; Below the main optical axis

Comments: Test points of this question: The imaging law of convex lens and its ** experiment

Test Center Comments: This question is an experiment of **convex lens imaging, and the candle flame examines the students' requirements for experimental operation Be sure to pay attention to the adjustment work before the experiment The surface of the convex lens and the light screen should be perpendicular to the orbit of the optical base; In order to make the image appear in the light screen, the center of the convex lens, candle flame and light screen should be roughly at the same height; In order to make the experimental conclusions universal, several sets of data should be measured for the same situation

The experimental principle of convex lens imaging is based on the refraction of light. Convex lenses have a magnifying effect. The details are as follows.

The experimental representation of convex lens imaging is an indication of the imaging law. The imaging law of the convex lens is as follows: when the object distance is within one time of the focal length, the upright and magnified virtual image is obtained; Between 1x and 2x focal lengths, a handstand, magnified real image is obtained; When outside of the double focal length, a handstand and zoomed out image is obtained.

The purpose of this experiment is to study and confirm this law.

**Experimental convex lens imaging experimental principle and procedure.

When the distance between the object and the convex lens is less than the focal length of the convex lens, the magnified image can be seen through the convex lens from the other side of the convex lens, which is like the intersection of the reverse extension line of the refracted light, which is a virtual image.

Convex lens into a real image: This situation can be subdivided into three cases. When the distance between the object and the lens is greater than the focal length of the convex lens, a real image can be formed on the other side of the convex lens.

When the object distance is greater than the focal length and less than 2 times the focal length, it becomes an inverted and magnified real image. When the object distance is equal to twice the focal length, it becomes an inverted real image with the same presence as the object. When the object distance is greater than 2 times the focal length, it becomes an inverted and reduced real image.

Experiment: **Convex lens imaging law,During the experiment, the candle is lit, so that the center of the candle flame, the convex lens, and the light screen is roughly in the same straight line and the same height, and the purpose is: to make the image of the candle flame appear on the light screen**.

Experimental Procedure.

Keep the position of the convex lens still, change the distance from the candle to the convex lens, adjust the position of the light screen, make the candle flame form a clear image on the light screen, and write down the object distance, image distance and imaging situation in different situations.

Place the candle in the focal point of the convex lens and look through the lens on the other side to create the image.

If no matter how you move the light screen during the experiment, you can't get the image on the light screen, the possible reasons are: the candle flame is in the focus, and the candle flame is in the focus; The center of the candle flame, convex lens, and light screen is not at the same height;

The distance between the candle flame and the convex lens is slightly larger than the focal length, and the imaging is far away, and the light screen of the light holder cannot be moved to this position.

Cover a part of the convex lens, the imaging properties remain unchanged, and the image becomes darker. When forming a real image, the smaller the object distance, the larger the image distance, and the larger the image.

Experimental Procedure.

Place the lens on the optical fixture coordinate ruler**, starting from the position of the lens, and chalk the position equal to the focal length and 2 times the focal length on the left and right rulers.

Light the candles and adjust their height so that the center of the candle flame, convex lens, and light screen is approximately the same height.

Place the candle as far away from the convex lens as possible, adjust the distance from the light screen to the lens, so that the candle flame becomes a clear image on the screen, observe the size of the image, forward and backward, and measure the distance between the candle and the convex lens, and between the convex lens and the light screen. Record the data in **.

Continue to approach the candle to the convex lens, observe whether the change of the image is magnified or reduced, whether it is upright or upright, the distance between the candle and the convex lens, the convex lens and the light screen is measured, and the data is recorded in **.

When the candle reaches a certain position, there is no image on the light screen, observe the image of the candle directly with the convex lens with your eyes, and fill in the distance between the candle and the convex lens, the image and the convex lens, such as enlargement or reduction, and the positive and backward of the image.