"Exploration - Imaging Laws of Convex Lenses" Common Optical Instruments PPT Courseware 3

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"Exploration - Imaging Laws of Convex Lenses" Common Optical Instruments PPT Courseware 3

Review the past and learn the new

1. Determine what kind of lens the following lenses belong to

2. Complete the following light path

Ask a question:

Activity: Use the convex lens in your hand to observe some objects around you and see what you find?

Teacher guides questions:

What are the characteristics of the image formed by an object passing through a convex lens, and what factors determine it?

Physical name:

(1) Object distance (u): the distance from the object to the optical center of the convex lens

(2) Image distance (v): the distance from the image to the optical center of the convex lens

(3) Focal length (f): the distance from the focus to the optical center of the convex lens

Conjectures and assumptions:

Students discuss.

Students come up with conjectures and hypotheses:

(1) Whether the image formed by a convex lens is enlarged or reduced may be related to the distance from the object to the convex lens.

(2) The inversion of the image formed by a convex lens may be related to whether the image and the object are on the same side of the convex lens.

Teachers encourage students to:

Students can use existing experimental equipment (light bench, light screen, candles, convex lenses with different focal lengths, matches) to design a feasible experimental plan to verify their conjectures.

Teacher tour guidance.

Let the experimental group communicate their experimental plans, and the teacher determines the most reasonable plan (as follows):

1. Select equipment related to the convex lens imaging experiment.

2. Let the luminous body pass through the convex lens to form an enlarged, reduced, or equal-sized image.

3. Measure the object distance and image distance during imaging. (Object distance: the distance from the object to the center of the convex lens. Image distance: the distance from the image to the center of the convex lens.)

Students do the following:

1 Use your own method to obtain the focal length of the convex lens (f=10cm).

2 Understand the light bench, and place the experimental equipment on the light bench in the order of candles, convex lenses, and light screens.

3. The candle flame passes through a convex lens to form a real image of equal size, and the object distance and image distance are recorded.

4. The candle flame passes through the convex lens to form a magnified real image, and the object distance and image distance are recorded.

5 The candle flame is transformed into a reduced real image through a convex lens, and the object distance and image distance are recorded.

6 The candle flame passes through the convex lens to form a magnified virtual image, and the object distance is recorded.

7 Do the above imaging process again.

Student Activities:

Based on the analysis of the experimental data of this group, the "laws of convex lens imaging" were summarized according to the questions raised at the beginning of the study.

The teacher summarizes the "rules" based on the students' answers (display animation):

1 When the object distance is greater than 2 times the focal length, an inverted and reduced real image will be formed.

2 When the object distance is greater than 1 times the focal length and less than 2 times the focal length, an inverted and magnified real image will be formed.

3 When the object distance is equal to 2 times the focal length, an inverted, equal-sized real image is formed.

4 When the object distance is less than 1 times the focal length, an upright, enlarged virtual image is formed.

Evaluation of this experiment:

Let students combine this experimental activity to find deficiencies in the plan for further improvement; and compare experimental results with conjectures to see the gaps and find reasons.

Exchange and cooperation:

Write an investigation report to explain the process and conclusions of the experiment as well as its application in production and life.

Application and improvement

Example 1 If an object passes through a convex lens to form an inverted and reduced real image, then the distance between the object and the convex lens satisfies _____________.

Example 2 Aiming a convex lens at the sun, you can get the smallest and brightest spot 20cm away from the convex lens. If you place an object 30cm in front of the lens, you can get a ( ) on the other side of the convex lens

A. Real image enlarged by inversion B. Real image reduced by inversion

C. Upright enlarged virtual image D. Upright reduced real image

Example 3 In the experiment of "Exploring the Laws of Imaging by Convex Lenses", we know that when an object forms a real image through a convex lens, the farther the object is from the lens, the closer the image is to the focus; if the object is far enough away from the lens (greater than 10f), the image formed will be The distance from the lens is approximately equal to the focal length of the lens.

Based on this, please design a simple method to estimate the focal length of a convex lens and briefly explain the experimental steps.

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For more information about the PPT courseware "Exploring the Imaging Rules of Convex Lenses and Common Optical Instruments", please click the Common Optical Instruments and Exploring the Imaging Rules of Convex Lenses ppt tag.

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Update Time: 2024-07-28

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