Polaroid-free Malus law verification experiment device

Abstract

The utility model discloses a Malus law verification experiment device without a polaroid. The Malus law verification experiment device comprises a light source generator, a first light reflecting body, a second light reflecting body and a light intensity sensing component, the first reflector is used for reflecting initial incident light emitted by the light source generator to the second reflector; the second reflector is used for secondarily reflecting the first reflected light reflected by the first reflector to the light intensity sensing component; initial incident light emitted by the light source generator is reflected by the first reflector to form linearly polarized light, and the linearly polarized light enters the second reflector at a Brewster angle; the second reflector can rotate around the propagation direction of the first reflected light, and in the rotation process, the intensity of light reflected by the second reflector can change along with the change of the rotation angle. According to the application, the discovery history of the Malus law is combined, the defect problem of a traditional Malus law verification scheme is solved, a polaroid is not used any more, the depolarization problem is avoided, and meanwhile the Malus law and the Brewster law can be verified at the same time through the experimental light path used in the application.

Description

Technical Field

[0001] The utility model relates to the technical field of teaching experiments, in particular to an experimental device for verifying Malus' law without a polarizer. Background Art

[0002] The polarization phenomenon of light is an important phenomenon in wave optics. Its essence is the asymmetry of the vibration direction of the light wave electric field with respect to the light propagation direction. It is an important sign that distinguishes transverse waves from longitudinal waves and is considered the fourth important "information dimension" parameter for describing the basic properties of electromagnetic waves in addition to intensity, wavelength, and phase [1]. The study of the polarization properties of light waves has deepened people's understanding of the laws of light propagation and the interaction between light and matter. Especially in recent years, various polarized light components, polarized light instruments, and polarized light technologies developed using the polarization of light have played an extremely important role in modern science and technology. For example, they have extensive applications in optical modulators, optical switches, optical metrology, stress analysis, optical information processing, optical communication, lasers, and quantum communication [2]. However, due to the abstract concept and strong theoretical nature of light polarization itself, and the lack of perceptual knowledge of polarized light among students, light polarization is a teaching difficulty in both middle schools and universities. Therefore, corresponding experimental devices must be used to help students deepen their understanding of polarization knowledge, thereby fully stimulating students' learning interest and improving teaching effects [3-4].

[0003] Among them, the most commonly used experimental device is the experimental instrument for verifying Malus' law [5-11]. Malus' law states that: when linearly polarized light with an intensity of I 0 passes through a polarizer, the relationship between the intensity I of the transmitted light and the angle α between the vibration direction of the incident linearly polarized light and the transmission direction of the polarizer is I = I 0 cos 2 α. The principle of the traditional experimental device for verifying Malus' law is as Figure 1 shown. Its basic steps are to let natural light vertically pass through two polarizers. The first polarizer P 1 is the polarizer, and the second polarizer P 2 is the analyzer. During the experiment, keep the first polarizer stationary, rotate the second polarizer while observing and recording the change in the intensity of the transmitted light, and verify Malus' law and the transverse wave nature of light by plotting the I-α curve between the light intensity and the angle between the two transmission directions.

[0004] Currently, all verification schemes for Malus' law are based on the selective absorption of light by polarizers. Only in different experimental schemes, different technical means such as CCD test systems, data acquisition cards, and single-chip microcontrollers are adopted for detecting the intensity of the transmitted light. These existing schemes mainly have the following technical drawbacks:

[0005] (1) All experimental setups for verifying Malus' law rely on polarizers and are premised on ideal polarizers. However, the artificial polarizers widely used in laboratories are made of organic polymer materials. When a polarizer is placed for too long, used frequently for a long time, or stored improperly, the degree of polarization of the polarizer will be significantly less than 1, that is, there is a certain degree of depolarization. If a depolarized polarizer is used to detect the polarization state and parameters of light, there will be a large error from the theoretical results of Malus' law. Especially when the angle is large, the deviation between theory and experiment reaches more than 20%, making it impossible to complete the relevant experimental verification. Therefore, Malus' law must be corrected in order to use depolarized polarizers to study the various properties of polarized light

[11] .

[0006] (2) The most primitive verification of Malus' law was not carried out using a polarizer. Because Malus' law was first accidentally discovered by the French physicist Malus in 1809 when he looked at the sunlight reflected from the windows of the Luxembourg Palace in Paris through a calcite crystal, and the earliest artificial polarizer was invented by the American inventor Land in 1928

[12] . Therefore, the verification of Malus' law based on polarizers is not the most primitive discovery process of this law.

[0007] (3) Existing experimental setups can only demonstrate Malus' law, while the polarization phenomenon can also be demonstrated using Brewster's law. Brewster's law was discovered by the British physicist Brewster in 1815. Its main content is: When natural light is reflected and refracted at the interface of two isotropic media, both the reflected light and the refracted light are partially polarized light. There are more perpendicular vibrations than parallel vibrations in the reflected light, and more parallel vibrations than perpendicular vibrations in the refracted light. When the reflected light is linearly polarized light, the angle of incidence of the light is the Brewster angle. Existing experimental setups use different optical paths to study Brewster's law and verify Malus' law respectively, which is not conducive to the systematic study of the polarization phenomenon.

[0008] References:

[0009] [1] Ren Liyong, Liang Jian, Qu Enshi, et al. Polarization optical imaging: Devices, technologies and applications (invited) [J]. Acta Photonica Sinica, 2022, 51(08): 96 - 131.

[0010] [2] Zhang Ting, Wu Wei, Sun Shihai. Interpreting cutting-edge technologies with college physics knowledge - from the polarization of light to quantum communication [J]. Physics and Engineering, 2024, 34(02): 19 - 24.

[0011] [3] Ge Shuibing. Teaching thinking and exploration based on the polarization of light [J]. Physics Teachers, 2022, 43(12): 89 - 90.

[0012] [4] Zhang Anguo, He Yan, Zhou Yuanyuan. Improvement of the Experiment on the Analysis of Polarized Light Characteristics [J]. Experiments in College Physics, 2017, 30(06): 57 - 60.

[0013] [5] Zhang Yitong, Li Fengguo. Verification of Malus' Law Using a Smart Phone [J]. Research on Education and Equipment, 2022, 38(05): 60 - 65.

[0014] [6] Yin Zhen, Chen Liping. Application of CCD Testing System in the Experiment of Verifying Malus' Law [J]. Journal of Gannan Normal University, 2004, (06): 84 - 85.

[0015] [7] Zhang Feigang, Cai Jianle, Hu Shuji. Experimental Study on Verifying Malus' Law with a Light Intensity Distribution Tester [J]. Research and Exploration in Laboratory, 2008, (01): 29 - 31.

[0016] [8] Wang Jianzhong, Huang Lin, Tang Yiwen. Experimental Design of "Verification of Malus' Law" Based on PASCO Sensors and NI Data Acquisition Cards [J]. Physics Experimentation, 2013, 33(02): 10 - 12 + 16.

[0017] [9] Gao Yijun, Wei Wei, Wang Xianfeng. Influence of the Polarization Characteristics of Semiconductor Lasers on the Experiment of Verifying Malus' Law [J]. Experiments in College Physics, 2019, 32(04): 23 - 26.

[0018]

[10] Hao Yunqi, Deng Wenhao, Miao Binchang, etc. Automatic Measurement System of "Malus' Law" Based on Photosensitive Resistor and Single Chip Microcomputer [J]. Electronic Test, 2021, (09): 12 - 14.

[0019]

[11] Ma Lei, Zhao Kun, Li Jixia, etc. Correction and Experimental Verification of Malus' Law for Depolarizing Sheets [J]. College Physics, 2010, 29(05): 58 - 61.

[0020]

[12] Yao Qijun. Optics Course. Higher Education Press, 2019. Utility Model Content

[0021] In order to solve the defect problems of traditional verification schemes of Malus' Law, the present utility model provides an experimental device for verifying Malus' Law without a polarizer.

[0022] The technical solution adopted by the present utility model to solve its technical problems is: providing an experimental device for verifying Malus' Law without a polarizer, which includes a light source generator, a first reflector, a second reflector, and a light intensity sensing component;

[0023] The light source generator is used to emit a collimated light source;

[0024] The first reflector is configured to reflect the initial incident light emitted by the light source generator to the second reflector;

[0025] The second reflector is configured to reflect the first reflected light reflected by the first reflector to the light intensity sensing component a second time;

[0026] The light intensity sensing component can make corresponding changes according to the change in the magnitude of the received light intensity;

[0027] Among them, the initial incident light emitted by the light source generator forms the first reflected light after being reflected by the first reflector. The first reflected light is linearly polarized light, and the first reflected light always enters the second reflector at the Brewster angle; moreover, the second reflector can rotate around the propagation direction of the first reflected light, and during the rotation process, the magnitude of the light intensity of the second reflected light formed after being reflected by the second reflector will change with the change in the rotation angle.

[0028] Further, the light source generator is a laser.

[0029] Further, both the first reflector and the second reflector are glass sheets. Among them, the first reflector is the first glass sheet, and the second reflector is the second glass sheet. It should be noted that the first reflector and the second reflector are not limited to glass sheets, and other objects with known refractive indices can also be selected.

[0030] Further, the experimental device for verifying Malus' law further includes an ammeter;

[0031] The light intensity sensing component is a silicon photocell. The ammeter is connected to the silicon photocell, and the silicon photocell can convert the received light energy into electrical energy and measure the current value through the ammeter.

[0032] Further, the experimental device for verifying Malus' law further includes a protractor;

[0033] The second reflector is mounted on the protractor, and the light intensity sensing component is fixed beside the protractor; the protractor can rotate around the propagation direction of the first reflected light and read out the rotation angle.

[0034] Further, the experimental device for verifying Malus' law further includes a cylindrical tube;

[0035] An opening is provided on the side wall at the bottom of the cylindrical tube. The first reflector is arranged at the bottom inside the cylindrical tube, and the protractor is arranged at the opening at the top of the cylindrical tube;

[0036] The initial incident light emitted by the light source generator passes through the opening of the bottom side wall of the cylindrical tube and then is emitted toward the first reflector, and the first reflected light reflected by the first reflector propagates along the axial direction of the cylindrical tube and then is emitted toward the second reflector.

[0037] Furthermore, the propagation direction of the first reflected light is vertically upward. Of course, the propagation direction of the first reflected light may not be vertically upward, but other directions, such as horizontal direction or other directions inclined relative to the horizontal plane, which can also achieve the same experimental effect. However, for ease of use, the propagation direction of the first reflected light is usually set to be vertically upward.

[0038] In the experimental device of the utility model, the angle at which the laser emits the laser and the inclination angles of the first glass sheet and the second glass sheet can be adjusted to ensure that the laser emitted by the laser can be incident on the first glass sheet at the Brewster angle. After being reflected by the first glass sheet, the laser will propagate to the second glass sheet in a vertically upward direction. After being reflected by the two glass sheets, the laser finally hits the silicon photocell wrapped in black cardboard. The photocurrent generated by the silicon photocell under light is measured by an ammeter to characterize the relative light intensity of the second reflected light. The experimental device of the utility model can accurately measure the relative light intensity value of the second reflected light when the second glass sheet rotates a corresponding angle around the propagation direction of the first reflected light, and verify Malus's law by fitting the measured data. At the same time, the experimental device combines the history of the discovery of Malus's law, solves the defects of the traditional Malus's law verification scheme, no longer uses polarizers, and avoids the depolarization problem.

[0039] The beneficial effects of the utility model are as follows:

[0040] (1) The experimental device of the present invention is an experimental exploration using the polarization characteristics of light when it is reflected on the surface of a glass sheet. Therefore, there is no depolarization problem mentioned in the background technology, and the theoretical calculation of the present invention is highly consistent with the experimental results.

[0041] (2) The experimental device of the utility model well combines the polarization characteristics of reflected light with the discovery history of Malus's law and the invention history of polarizers, which can enable students to have a deeper understanding of the discovery, development and application of light polarization.

[0042] (3) The experimental device of the utility model can verify Malus's law by using only two glass sheets. The experimental device is simpler and the experimental principle is clear and easy to understand. More importantly, the same experimental optical path can be used to verify Malus's law and Brewster's law at the same time. The systematic experimental plan and experimental principle enable students to understand the characteristics of polarized light more thoroughly. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the experimental device for verifying Malus' law in the traditional way;

[0044] Figure 2 It is an experimental device for verifying Malus' law without a polarizer provided by the present utility model;

[0045] Figure 3 is Figure 2 the working schematic diagram;

[0046] Figure 4 It is a schematic diagram of the light reflected by the first glass sheet in the experimental device of the present utility model;

[0047] Figure 5 It is a schematic diagram of the second glass sheet before and after rotating around the z-axis in the figure in the experimental device of the present utility model;

[0048] Figure 6 It is a schematic diagram of the optical path change before and after the angle disc rotates in the experimental device of the present utility model;

[0049] Figure 7 It is a circuit diagram of the silicon photocell measuring the relative light intensity in the experimental device of the present utility model;

[0050] Figure 8 It is a fitting diagram of experimental data during the process of verifying Malus' law in the experimental device of the present utility model;

[0051] In the figure, the markings are: 1 - the first glass sheet, 2 - the second glass sheet, 3 - the silicon photocell, 4 - the angle disc, 5 - the ammeter, 6 - the laser, 7 - the cylindrical barrel, 8 - the bottom plate, L1 - the initial incident light, L2 - the first reflected light, L3 - the second reflected light. Specific embodiments

[0052] The following further details the present utility model in combination with specific embodiments, but the implementation manners of the present utility model are not limited thereto.

[0053] The present utility model provides an experimental method for verifying Malus' law without a polarizer, which uses two reflectors to reflect the collimated light source in sequence; wherein, the first reflected light formed after the collimated light source is reflected by the first reflector is linearly polarized light, and the first reflected light always enters the second reflector at the Brewster angle. The second reflector can rotate around the propagation direction of the first reflected light. During the rotation process, the light intensity of the second reflected light formed after being reflected by the second reflector will change with the change of the rotation angle. Record the relationship between the rotation angle of the second reflector and the light intensity of the second reflected light to verify whether the relationship between the light intensity of the second reflected light and the rotation angle of the second reflector satisfies Malus' law.

[0054] Further, the method for verifying Malus' law further includes: receiving the second reflected light and generating a photocurrent therewith to characterize the light intensity of the second reflected light.

[0055] Among them, receiving the second reflected light and generating a photocurrent therewith to characterize the light intensity of the second reflected light specifically includes: using a silicon photocell to receive the second reflected light, converting the light energy of the received second reflected light into a photocurrent, and then displaying the current magnitude of the photocurrent through an ammeter, thereby indirectly characterizing the light intensity of the second reflected light.

[0056] Record the relationship between the rotation angle of the second reflector and the light intensity of the second reflected light, specifically: record the rotation angle of the second reflector and the corresponding photocurrent magnitude, and form a two-dimensional relationship image.

[0057] Based on the above method for verifying Malus' law, the present utility model further provides an experimental device for verifying Malus' law without a polarizer, see Figure 2 which includes a light source generator, a first reflector, a second reflector, and a light intensity sensing component.

[0058] Among them, the light source generator is a laser 6, which is used to emit a collimated light source.

[0059] Both the first reflector and the second reflector are made of glass sheets. Among them, the first reflector is the first glass sheet 1, and the second reflector is the second glass sheet 2. The first glass sheet 1 is used to reflect the initial incident light emitted by the laser 6 to the second glass sheet 2. The second glass sheet 2 is used to reflect the first reflected light reflected by the first glass sheet 1 to the light intensity sensing component for a second time. It should be noted that the first reflector and the second reflector are not limited to glass sheets. In some embodiments, other objects with known refractive indices can also be selected.

[0060] The light intensity sensing component can make corresponding changes according to the change in the received light intensity.

[0061] Among them, see Figure 3 wherein the initial incident light L1 emitted by the light source generator is reflected by the first glass sheet 1 to form a first reflected light L2. The first reflected light L2 is linearly polarized light, and the first reflected light L2 always enters the second glass sheet 2 at the Brewster angle; and the second glass sheet 2 can rotate around the first reflected light L2, and during the rotation process, the light intensity of the second reflected light L3 formed after being reflected by the second glass sheet 2 will change with the change in the rotation angle.

[0062] In some embodiments, see Figure 2, the experimental device for verifying Malus' law of the present utility model further includes an ammeter 5. The light intensity sensing component is a silicon photocell 3, and the ammeter 5 is connected to the silicon photocell 3. The silicon photocell 3 can convert the received light energy into electrical energy and measure the current value through the ammeter 5. Preferably, the ammeter 5 is a digital display ammeter, which can display the measured current value digitally.

[0063] In some embodiments, referring to Figure 2 , the experimental device for verifying Malus' law of the present utility model further includes a protractor 4. The second glass sheet 2 is mounted on the protractor 4, and the silicon photocell 3 is fixed beside the protractor 4. The protractor 4 is used to read the angle of rotation of the second glass sheet 2 around the propagation direction of the first reflected light L2.

[0064] In some embodiments, referring to Figure 2 , the experimental device for verifying Malus' law further includes a cylindrical barrel 7 and a bottom plate 8. The cylindrical barrel 7 is fixed on the bottom plate 8, the axis of the cylindrical barrel 7 is perpendicular to the bottom plate 8, and an opening is provided on the side wall at the bottom of the cylindrical barrel 7. The first glass sheet 1 is arranged in the center of the cylindrical barrel 7 and corresponds to the opening on the side wall at the bottom of the cylindrical barrel 7. The protractor 4 is arranged at the opening at the top of the cylindrical barrel 7 and can rotate around the propagation direction of the first reflected light L2. Among them, the initial incident light L1 emitted by the laser 6 passes through the opening on the side wall at the bottom of the cylindrical barrel 7 and then irradiates the first glass sheet 1. The first reflected light L2 after being reflected by the first glass sheet 1 propagates along the central axis direction of the cylindrical barrel 7 and then irradiates the second glass sheet 2, and is incident on the second glass sheet 2 at the Brewster angle.

[0065] Moreover, in the above experimental device, the angle of the laser emitted by the laser 6 and the tilt angles of the first glass sheet 1 and the second glass sheet 2 can be adjusted to ensure that the laser emitted by the laser 6 can be incident on the first glass sheet 1 at the Brewster angle, and at the same time, the second glass sheet 2 can be accurately adjusted to have the same tilt angle as the first glass sheet 1. And the laser 6, the first glass sheet 1, and the second glass sheet 2 are all equipped with angle measuring devices (refer to Figure 2 ) to assist the three in angle adjustment respectively.

[0066] When conducting an experiment using the experimental device for verifying Malus' law of the present utility model, place the bottom plate 8 on the workbench surface. When the laser generated by the laser 6 is from Figure 3After emitting from point A in the figure, the initial incident light L1 enters the first glass sheet 1 at the center of the cylindrical tube 7 through the bottom opening of the cylindrical tube 7. After being reflected at point B in the figure, the first reflected light L2 is incident on the second glass sheet 2 in the vertically upward direction. After being reflected for the second time at point C in the figure, the second reflected light L3 is finally incident on point D in the figure and is received by the linear silicon photocell 3. Subsequently, the current generated by the silicon photocell 3 can be measured through the ammeter 5, thereby characterizing the relative light intensity of the second reflected light L3. Among them, rotating the angle dial 4 will cause the intensity of the second reflected light L3 to change, and the photocurrent will also change accordingly. Recording the rotation angle of the angle dial 4 and the corresponding photocurrent (i.e., relative light intensity) can verify whether the relationship between the light intensity of the second reflected light L3 and the rotation angle of the angle dial 4 satisfies Malus' law.

[0067] The principle of the experimental device for verifying Malus' law of the present utility model is as follows:

[0068] (Ⅰ) Brewster's law:

[0069] When natural light is reflected and refracted at the dielectric interface, when the incident angle is a certain specific angle, its reflected light is linearly polarized light, and its vibration direction is perpendicular to the plane of incidence (the plane passing through the incident light and the reflected light). This specific angle is called the Brewster angle or the polarization angle. The electric vector of the incident light can be decomposed into a parallel component A p parallel to the plane of incidence and a perpendicular component A s perpendicular to the plane of incidence. From Fresnel's formula, it is known that the parallel component of the electric vector is A p :

[0070]

[0071] In formula (1), A′ p1 is the parallel component of the reflected light, A p1 is the parallel component of the incident light, i 1 is the incident angle, and i 2 is the refraction angle;

[0072] When i 1 + i 2 = 90°, in formula (1), tan(i 1 + i 2 ) → ∞, so A p ′ 1 = 0. At this time, the reflected light has no parallel component, and i 1 is the Brewster angle. From the refraction law, we have:

[0073]

[0074] In formula (2), n 1 and n 2are the refractive indices of air and glass, which are 1 and 1.515 respectively; i 1 is the incident angle and is equal to the Brewster angle, i 2 is the refraction angle;

[0075] After calculation, it is obtained that: i 1 = 56.34°.

[0076] (Ⅱ) Polarization and depolarization:

[0077] In the traditional experimental device for verifying Malus' law, see Figure 1 . Natural light becomes linearly polarized light after passing through the first polarizer. The vibration direction of the linearly polarized light is consistent with the transmission direction of the first polarizer. At this time, the first polarizer acts as a polarizer. When using the second polarizer to detect the polarization of light, the second polarizer acts as a depolarizer at this time.

[0078] In the experimental device of the present utility model, the first glass sheet 1 is equivalent to a polarizer, and the second glass sheet 2 is equivalent to a depolarizer. The reflection process of light by the first glass sheet 1 is as Figure 4 shown. According to Brewster's law, it can be known that when the laser is incident on the first glass sheet 1 at the Brewster angle i 1 (i.e., i 1 = 56.34°), the reflected light is linearly polarized light with only a vertical component. To ensure that the propagation direction of the reflected light of the first glass sheet 1 is vertically upward, considering that the refractive index of the selected glass sheet is 1.515, after calculation, it can be obtained that the angle between the initial incident light L1 and the horizontal plane should be set to θ = 22.68°. Therefore, the angle of the laser emitted by the laser 6 needs to be adjusted to 22.68° with respect to the horizontal plane.

[0079] In the experimental device of the present utility model, the angle scale 4 above the cylindrical barrel 7 can rotate freely and drive the second glass sheet 2 to rotate together. The state where the first glass sheet 1 and the second glass sheet 2 are parallel to each other is defined as the initial position, as Figure 5 shown in (a) of Figure 5 . Taking the center point of the disc as the origin O and the glass sheet as the stationary reference system, a three-dimensional coordinate system is established. Among them, the yOz plane is the reflection plane of the second glass sheet 2, which is the same as the reflection plane of the first glass sheet 1, and the xOz plane is perpendicular to it. If the angle scale 4 is rotated by α, the reflection plane of the second glass sheet 2 becomes y'Oz, and there will be an angle α with the reflection plane yOz of the first glass sheet 1, as

[0080] shown in (b) of Figure 6As shown in (a), the first reflected light L2 of the first glass sheet 1 is incident upward in the vertically upward direction onto the second glass sheet 2. Since the first glass sheet 1 and the second glass sheet 2 are parallel to each other at this time, the incident angle of the first reflected light L2 entering the second glass sheet 2 is still the Brewster angle i. 1 . Similarly, according to Brewster's law, the parallel component of the second reflected light L3 parallel to the reflection plane yOz is 0, and only the perpendicular component exists. Rotating the angle disk 4 can change the angle α between the second glass sheet 2 and the reflection plane of the first glass sheet 1, and the second glass sheet 2 will act as an analyzer.

[0081] (Ⅲ) Explanation of the light intensity change:

[0082] Let the amplitude of the linearly polarized light (i.e., the first reflected light L2) obtained after reflection by the first glass sheet 1 be A. 0 , taking the rotation angle of the second glass sheet 2 as α and the second glass sheet 2 as the reference plane, the parallel component and the perpendicular component of the amplitude of the first reflected light L2 are respectively:

[0083] A p2 = A 0 sinα, A s2 = A 0 cosα (3)

[0084] The linearly polarized light (i.e., the first reflected light L2) is incident on the second glass sheet 2 at the Brewster angle i. 1 The parallel component A′ of the amplitude of the second reflected light L3 p2 = 0, and i 1 + i 2 = 90°. According to the Fresnel formula, the ratio of the perpendicular vibration component of the second reflected light L3 to the first reflected light L2 is:

[0085]

[0086] In formula (4), i 1 is the incident angle when the first reflected light L2 is incident on the second glass sheet 2, and i 2 is the refraction angle after the first reflected light L2 is incident on the second glass sheet 2;

[0087] Combining (3) and (4), and considering that the light intensity is positively correlated with the square of the amplitude, we can obtain:

[0088]

[0089] where I L3 is the intensity of the final reflected light (i.e., the intensity of the second reflected light L3), and I C is related to the incident light intensity I L2(i.e., the intensity of the first reflected light L2), and α is the angle of rotation of the angle dial 4. It can be seen that the light intensity of the linearly polarized light after reflection by the second glass sheet 2 is proportional to cos 2 α, which is Malus' law. When α = 0°, the light intensity of the reflected light from the second glass sheet 2 reaches the maximum. When α = 90°, the light intensity of the reflected light from the second glass sheet 2 is zero, that is, extinction occurs.

[0090] (IV) Measurement of relative light intensity

[0091] As Figure 7 shown, the experimental device of the present utility model uses a linear silicon photocell 3 to receive the second reflected light L3 of the final second glass sheet 2, and is connected to an ammeter 5 to measure the current magnitude. The linear silicon photocell 3 is composed of a PN junction. When the PN junction receives photons, electron or hole migration occurs, thereby generating a photocurrent, and the magnitude of the current has a strong linear relationship with the light intensity of the received light. The relative light intensity of the reflected light can be obtained from the measured current value.

[0092] (V) Determination of other parameters

[0093] The refractive index is measured using an Abbe refractometer. The Abbe refractometer is an instrument that can measure the refractive index and average dispersion of transparent, semi-transparent liquids or solids (mainly for measuring transparent liquids). It can measure that the refractive indices of the first glass sheet 1 and the second glass sheet 2 in the present utility model are both 1.515.

[0094] Regarding the comparison between theory and experiment:

[0095] In the experiment, with a gradient of 10°, the angle dial 4 is rotated to measure the relative light intensity value of the second reflected light L3 at the corresponding angles. Figure 8 shows the experimental data and the theoretical fitting curve. The fitting result is: I L3 = 1.194cos 2 α, and the fitting degree: R 2 = 0.984. It can be seen that this fitting result has a high credibility. And when the angle is close to 90°, the relative light intensity drops to 0, and extinction occurs, which very accurately verifies Malus' law.

[0096] Regarding the demonstration of Fresnel's formula and Brewster's law:

[0097] The incident angle on the first glass 1 is adjusted to a non-Brewster angle, and the incident angle of the second glass sheet 2 is still maintained at the Brewster angle. According to Fresnel's formula, the reflected light from the first glass sheet 1 is partially polarized light at this time. When the angle dial 4 at the top of the cylindrical barrel 7 is rotated, since the light incident on the second glass sheet 2 is not completely linearly polarized light, the reflected light will not show extinction during the rotation process, thus verifying Fresnel's formula and Brewster's law.

[0098] In summary, compared with the traditional experimental device for verifying Malus' law, the experimental device of the present utility model has the following beneficial effects:

[0099] (1) The experimental device of the present utility model conducts experimental exploration by utilizing the polarization characteristics of light when it is reflected on the surface of a glass sheet. Therefore, there is no depolarization problem mentioned in the background art, and the theoretical calculation of the present utility model is highly consistent with the experimental results.

[0100] (2) The experimental device of the present utility model combines well the polarization characteristics of reflected light, the discovery history of Malus' law, and the invention history of polarizing plates, enabling students to understand more deeply the discovery, development, and application of light polarization.

[0101] (3) The experimental device of the present utility model can verify Malus' law by using only two glass sheets. The experimental device is more simple, and the experimental principle is also clear and easy to understand. Particularly importantly, Malus' law and Brewster's law can be verified simultaneously using the same experimental optical path. The systematic experimental scheme and experimental principle enable students to understand the characteristics of polarized light more thoroughly.

[0102] The above description is only the preferred embodiment of the present utility model and is not intended to limit the present utility model. For those skilled in the art, the present utility model can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. An experimental device for verifying Malus's law without polarizer, characterized in that: It includes a light source generator, a first light reflector, a second light reflector and a light intensity sensing component; The light source generator is used to emit a collimated light source; The first reflector is used to reflect the initial incident light emitted by the light source generator to the second reflector; The second reflector is used to re-reflect the first reflected light reflected by the first reflector to the light intensity sensing component; The light intensity sensing component can make corresponding changes according to the changes in the intensity of the received light; The initial incident light (L1) emitted by the light source generator is reflected by the first reflector to form a first reflected light (L2), the first reflected light (L2) is linearly polarized light, and the first reflected light (L2) is always incident on the second reflector at a Brewster angle; and the second reflector can rotate around the propagation direction of the first reflected light (L2), and during the rotation process, the light intensity of the second reflected light (L3) formed after being reflected by the second reflector changes with the change of the rotation angle.

2. The Malus law verification experimental device without polarizer according to claim 1, characterized in that: The light source generator is a laser (6).

3. The Malus law verification experimental device without polarizer according to claim 1, characterized in that: The first reflector and the second reflector are both glass sheets, wherein the first reflector is a first glass sheet (1) and the second reflector is a second glass sheet (2).

4. The Malus law verification experimental device without polarizer according to claim 1, characterized in that: The Malus law verification experimental device also includes an ammeter (5); The light intensity sensing component is a silicon photocell (3), and the ammeter (5) is connected to the silicon photocell (3). The silicon photocell (3) can convert the received light energy into electrical energy and measure the current value via the ammeter (5).

5. The Malus law verification experimental device without polarizer according to claim 1, characterized in that: The Malus law verification experimental device further comprises an angle plate (4); The second reflector is mounted on the angle disc (4), and the light intensity sensing component is fixed on the side of the angle disc (4); the angle disc (4) is capable of rotating around the propagation direction of the first reflected light (L2) and reading out the rotation angle.

6. The Malus law verification experimental device without polarizer according to claim 5, characterized in that: The Malus law verification experimental device also includes a cylindrical barrel (7); The side wall of the bottom of the cylindrical tube (7) is provided with an opening, the first reflector is arranged at the bottom of the cylindrical tube (7), and the angle plate (4) is arranged at the opening at the top of the cylindrical tube (7); The initial incident light (L1) emitted by the light source generator passes through the opening of the bottom side wall of the cylindrical tube (7) and then is emitted toward the first reflector, and the first reflected light (L2) reflected by the first reflector propagates along the axial direction of the cylindrical tube (7) and then is emitted toward the second reflector.

7. The Malus law verification experimental device without polarizer according to any one of claims 1 to 6, characterized in that: The propagation direction of the first reflected light (L2) is vertically upward.

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