Optical detection method, optical detection device and optical experiment teaching appliance

Abstract

The invention discloses an optical detection method and device and a light experiment teaching appliance, and belongs to the technical field of optical detection. The method comprises the following steps: S1, constructing an optical path; s2, adjusting the width of a slit of the optical screen to enable an observer to observe diffraction fringes on the optical screen, adjusting the position of the observer to enable the observer to align zero-order diffraction fringes observed by the transmitted light of the monochromatic light source passing through the grating to the slit; s3, turning on the laser, adjusting the position of the laser in the optical axis direction, and enabling a diffraction fringe real image of the laser passing through the grating to coincide with a diffraction fringe virtual image observed by transmitted light of an observer passing through the grating opposite to the monochromatic light source; s4, the position of the laser is kept, and a shading screen is placed on the side, close to an observer, of the optical screen; s5, the distance x between the grating and the light screen and the distance Y between the first-level diffraction fringes or the second-level diffraction fringes of the laser on the shading screen are obtained; and S6, according to x and Y, utilizing a Fraunhofer diffraction law to calculate a wavelength or a grating constant.

Description

Technical Field

[0001] The invention belongs to the technical field of optical detection, and in particular relates to an optical detection method and detection device and an optical experiment teaching tool. Background Art

[0002] Measuring the wavelength of light with a spectrometer is a classic physics experiment in teaching. Its purpose is to understand the characteristics of diffraction gratings and their applications in spectral instruments and to learn how to adjust and use spectrophotometers. The principle is that when a beam of parallel light is incident vertically on the grating, a group of alternating light and dark diffraction fringes are generated, such as Figure 1 As shown in Figure 1, the Fraunhofer diffraction principal maximum is determined by the following formula: d*sinΦ=kλ. As long as the diffraction angle of a spectral line of any order is measured, the wavelength of the light wave can be calculated.

[0003] In the formula: d: grating constant; d=a+b; Φ: diffraction angle; k: main maximum order; k=0, 1,...; grating constant d=a+b refers to the distance between two adjacent grating slits, a refers to the slit width of the grating, and b refers to the opaque width of the grating.

[0004] like Figure 2 The figure shows a schematic diagram of a spectrometer. The spectrometer includes a scale plate, a collimator, a telescope, a grating, and a sodium monochromatic light source. The collimator is used to generate parallel light, the telescope is used to receive diffracted light, and the scale plate is used to read the angle value.

[0005] There are several problems in using a spectrometer to measure the wavelength of light or the grating constant. First, the instrument adjustment is relatively complicated, and it takes a lot of time to level the spectrometer, and skilled adjustment techniques are required. Second, the spectrometer platform can only accommodate one person to observe the diffraction pattern, which is not conducive to teaching demonstrations. Summary of the invention

[0006] In order to solve the above problems, the embodiments of the present invention provide an optical detection method and detection device and optical experiment teaching tools. Compared with using a spectrometer to measure the wavelength of light waves or grating constants, the operation is simpler; at the same time, the detection results are accurate, which is convenient for multiple people to observe at the same time. The interference and diffraction phenomena of light are direct manifestations of the wave nature of light. When the light source and the observation screen are infinitely far away from the diffraction screen, the diffraction phenomenon is called the Fraunhofer diffraction experiment. Using a transmission grating as a diffraction screen, the wavelength of visible light is measured using the Fraunhofer diffraction law. The conditions for forming diffraction bright fringes are: (1); This formula is called the grating equation, where the angle θ is the diffraction angle, λ is the wavelength of the light wave, k is the spectral order, and d=a+b is the grating constant. Because the diffraction bright fringes are actually the diffraction phenomenon of the light source slit, it is a sharp and thin bright line, so it is also called spectral line.

[0007] When k is equal to 0, light of any wavelength satisfies equation (1), that is, in the direction of θ=0. Spectral lines of various wavelengths overlap to form a bright zero-order spectrum. For other values ​​of k, different spectra appear in different directions, and the two sets of spectra corresponding to the positive and negative sets of k are symmetrically distributed on both sides of the zero-order spectrum. If the grating constant is known, the diffraction angle θ and the corresponding spectral order k of a certain spectral line are measured in the experiment, then the wavelength of the spectral line can be calculated from equation (1).

[0008] like Figure 3 As shown, according to the single-slit diffraction law of the grating, the single-slit diffraction stripes should be distributed on the right side of the grating 3. When the observer 5 is on the same side as the monochromatic light source 1, the diffraction stripes can be observed on the light screen 2 on the right side of the grating 3. However, the present invention takes the opposite approach and adopts an unconventional method. If the observer 5 looks at the monochromatic light source 1 against the diffraction light on the right side of the grating 3, the virtual image of the diffraction stripes can be seen on the right side of the light screen 2. Since the virtual image cannot be directly imaged on the light screen 2, a laser 4 is placed at the position of the observer 5. The laser 4 forms laser diffraction stripes on the right side of the light screen 2 through the grating 3. At this time, the observer 5 looks at the monochromatic light source 1 through the grating 3, and can simultaneously observe the virtual image of the monochromatic light diffraction stripes and the real image of the laser diffraction stripes. Move the laser 4. When the real image of the laser diffraction stripes and the virtual image of the monochromatic light diffraction stripes coincide, the diffraction angle of the monochromatic light source on the grating 3 is equal to the diffraction angle of the laser 4 on the grating 3, both of which are θ. The technical scheme is as follows: In one aspect, an embodiment of the present invention provides an optical detection method, the method comprising the following steps: S1: build the optical path; S2: Adjust the width of the slit of the light screen 2 so that the observer 5 can observe the diffraction fringes on the light screen 2, and adjust the position of the observer 5 in the direction of the optical axis so that the zero-order diffraction fringes observed by the observer 5 against the transmission light of the monochromatic light source 1 after passing through the grating 3 are aligned with the slit; S3: Turn on the laser 4, and adjust the position of the laser 4 in the direction of the optical axis so that the real image of the diffraction stripes of the laser passing through the grating 3 coincides with the virtual image of the diffraction stripes observed by the observer 5 after the transmitted light of the monochromatic light source 1 passes through the grating 3; S4: Keep the position of the laser 4 and place a light shielding screen 6 on the side of the light screen 2 close to the observer 5; S5: Obtain the distance x between the grating 3 and the light screen 2 and the distance Y between the first-order or second-order diffraction fringes of the laser 4 on the light shielding screen 6; S6: Calculate the wavelength or grating constant based on x and Y using the Fraunhofer diffraction law; The optical path includes a monochromatic light source 1, a light screen 2, a grating 3 and a laser 4. The light screen 2 is provided with a slit with adjustable width. The monochromatic light source 1, the light screen 2, the grating 3 and the laser 4 are arranged in sequence along the optical axis. The light screen 2 and the grating 3 are both perpendicular to the optical axis. The observer 5 is located on the side of the grating 3 away from the light screen 2. The monochromatic light source 1, the slit, the grating 3 and the laser 4 are at the same height, and the laser of the laser 4 is parallel to the optical axis.

[0009] If the grating constant needs to be detected, a monochromatic light source 1 with a known wavelength is used; if the wavelength needs to be detected, a grating 3 with a known grating constant is used.

[0010] Wherein, in step S6, calculation is performed according to formula I: (I) in, is the diffraction angle, is the wavelength, k is 1 or 2, d is the grating constant, , y=Y / 2.

[0011] Preferably, in step S5, the distance between the first-order diffraction fringes of the laser 4 on the light shielding screen 6 is obtained, and then in step S6, it is calculated according to formula II: (II).

[0012] Furthermore, the optical detection method provided by the present invention further includes: adjusting the distance between the grating 3 and the light screen 2 to perform multiple detections, and calculating an average value of the multiple detections.

[0013] Wherein, when conducting the wavelength teaching and detection test, the monochromatic light source 1 is a low-pressure sodium monochromatic light source, and the x is 10-20 cm.

[0014] On the other hand, an embodiment of the present invention further provides an optical detection device, which includes a monochromatic light source 1, a light screen 2, a grating 3, a laser 4, a shading screen 6 and a distance detection tool, wherein the light screen 2 is provided with a slit with adjustable width, the monochromatic light source 1, the light screen 2, the grating 3 and the laser 4 are arranged in sequence along the optical axis, the light screen 2 and the grating 3 are perpendicular to the optical axis, the observer 5 is located on the side of the grating 3 away from the light screen 2, the monochromatic light source 1, the slit, the grating 3 and the laser 4 are at the same height, the laser of the laser 4 is parallel to the optical axis, and the shading screen 6 can shield the light screen 2; wherein the light screen 2, the grating 3 and the laser 4 can be adjusted in the direction of the optical axis; The width of the slit allows the observer 5 to observe diffraction fringes on the light screen 2; the distance between the observer 5 and the grating 3 allows the zero-order diffraction fringes observed by the observer 5 after the transmitted light from the monochromatic light source 1 through the grating 3 to be aligned with the slit; the distance between the laser 4 and the grating 3 allows the real image of the diffraction fringes of the laser passing through the grating 3 to coincide with the virtual image of the diffraction fringes observed by the observer 5 after the transmitted light from the monochromatic light source 1 through the grating 3; during detection, the shading screen 6 is placed on the side of the light screen 2 close to the observer 5; the distance detection tool is used to detect the distance between the light screen 2 and the grating 3 and the distance between the first-order or second-order diffraction fringes of the laser 4 on the shading screen 6.

[0015] Specifically, the monochromatic light source 1, light screen 2, grating 3 and laser 4 in the embodiment of the present invention are all arranged on an optical bench platform, and the position parameters of the light screen 2 and the grating 3 can be read on the optical bench platform to obtain the distance between the light screen 2 and the grating 3; the distance detection tool is a vernier caliper for obtaining the distance between the first-order or second-order diffraction stripes of the laser 4 on the shading screen 6, and the shading screen 6 is white paper.

[0016] On the other hand, an embodiment of the present invention further provides an optical experiment teaching tool, comprising the aforementioned optical detection device, for detecting wavelength.

[0017] Specifically, the monochromatic light source 1 in the embodiment of the present invention is a low-pressure sodium monochromatic light source, the distance between the light screen 2 and the grating 3 is 10-20 cm, and the grating constant d of the grating 3 is 1 / 300 mm.

[0018] The beneficial effects of the technical solution provided by the embodiment of the present invention are as follows: the patent reduces the complicated instrument adjustment process caused by measuring the wavelength of monochromatic light with a spectrometer, visualizes the optical path adjustment and observation, and cleverly utilizes the overlap of virtual and real images. In teaching experiments, students have a deeper understanding of physical principles such as the imaging laws of virtual and real images, the single-slit diffraction law, and the reversible principle of the optical path. At the same time, the measurement results of this method are more accurate than those of the spectrometer measuring the wavelength of monochromatic light, and it is also convenient for multiple people to observe. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a schematic diagram of the principle of light wave diffraction; Figure 2 It is a schematic diagram of the structure of an experimental device for measuring the wavelength of light waves using an existing spectrometer; Figure 3 is a schematic structural diagram of an optical detection device provided by an embodiment of the present invention; Figure 4 is a schematic diagram of x and Y; Figure 5 It is a flow chart of the optical detection method provided by an embodiment of the present invention.

[0019] Among them, 1 is a monochromatic light source, 2 is a light screen, 3 is a grating, 4 is a laser, 5 is an observer, 6 is a light shielding screen, 7 is the light of the monochromatic light source, and 8 is the laser of the laser. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] Example 1 See also Figure 3 and 4 Embodiment 1 provides an optical detection device, which includes a monochromatic light source 1, a light screen 2, a grating 3, a laser 4, a shading screen 6, an optical bench platform, and a distance detection tool. The light screen 2 is provided with a slit with adjustable width; specifically, a 2mm small hole is provided in the middle of the light screen 2; a slit is provided at the small hole, and a slit adjustment handwheel for adjusting the slit width is provided on the light screen 2, which is a conventional structure. The monochromatic light source 1, the light screen 2, the grating 3 and the laser 4 are arranged in sequence along the optical axis and are all arranged on the optical bench platform. The light screen 2 and the grating 3 are perpendicular to the optical axis, and the observer 5 is located on the side of the grating 3 away from the light screen 2. The monochromatic light source 1, the slit, the grating 3 and the laser 4 are at the same height, and the laser of the laser 4 is parallel to the optical axis (as close as possible). The shading screen 6 can shield the light screen 2, which is specifically white paper. Among them, the light screen 2, the grating 3 and the laser 4 can be adjusted in the direction of the optical axis.

[0022] The width of the slit allows the observer 5 to observe diffraction fringes on the light screen 2. The distance between the observer 5 and the grating 3 (achieved by adjusting the position of the observer 5) allows the zero-order diffraction fringes observed by the observer 5 against the monochromatic light source 1 after the transmitted light passes through the grating 3 to be aligned with the slit. The distance between the laser 4 and the grating 3 (achieved by adjusting the position of the laser 4) allows the real image of the diffraction fringes of the laser passing through the grating 3 to coincide with the virtual image of the diffraction fringes observed by the observer 5 against the monochromatic light source 1 after the transmitted light passes through the grating 3 (at this time, the distance between the positive and negative first-order or second-order diffraction fringes after the laser passes through the grating 3 is equal to the distance between the positive and negative first-order or second-order diffraction fringes of the virtual image of the diffraction fringes of the monochromatic light observed by the eyes). During the detection (i.e., step S4), the light shielding screen 6 is placed on the side of the light screen 2 close to the observer 5. The distance detection tool is used to detect the distance between the first-order or second-order diffraction fringes of the laser 4 on the light shielding screen 6, which can be specifically a vernier caliper. The position parameters of the light screen 2 and the grating 3 are read through the optical bench platform to obtain the distance between the light screen 2 and the grating 3 . Example 2 Embodiment 2 provides a light experiment teaching tool, including the optical detection device provided in embodiment 1, for detecting wavelength. Specifically, the monochromatic light source 1 in the embodiment of the present invention is a low-pressure sodium monochromatic light source, the distance between the light screen 2 and the grating 3 is 10-20cm, and the grating constant d of the grating 3 is 1 / 300mm.

[0023] Example 3 See also Figure 5 Embodiment 3 provides an optical detection method, the method comprising the following steps: S1: Construct an optical path as described in Example 1.

[0024] S2: The width of the slit of the light screen 2 is adjusted so that the observer 5 can observe the diffraction fringes on the light screen 2. The position of the observer 5 is adjusted in the direction of the optical axis so that the zero-order diffraction fringes observed by the observer 5 after the transmitted light of the monochromatic light source 1 passes through the grating 3 are aligned with the slit. At this time, the laser 4 is turned off.

[0025] S3: Turn on the laser 4, and adjust the position of the laser 4 in the direction of the optical axis so that the real image of the diffraction stripes of the laser passing through the grating 3 coincides with the virtual image of the diffraction stripes observed by the observer 5 after the transmitted light of the laser passing through the grating 3 against the monochromatic light source 1. At this time, the distance between the positive and negative first-order or second-order diffraction stripes after the laser passes through the grating 3 is equal to the distance between the positive and negative first-order or second-order diffraction stripes of the virtual image of the diffraction stripes of the monochromatic light observed by the eyes.

[0026] Specifically, the brighter real image of the diffraction stripes of the laser passing through the grating 3 is made to coincide with the brighter virtual image of the diffraction stripes observed by the observer 5 after the transmitted light passes through the grating 3 against the monochromatic light source 1. More specifically, the real image of the first-order or second-order diffraction stripes of the laser passing through the grating 3 is made to coincide with the virtual image of the first-order or second-order diffraction stripes observed by the observer 5 after the transmitted light passes through the grating 3 against the monochromatic light source 1, such as the first-order coincides with the first-order, the first-order coincides with the second-order, etc. More preferably, the real image of the first-order diffraction stripes of the laser passing through the grating 3 is made to coincide with the virtual image of the first-order diffraction stripes observed by the observer 5 after the transmitted light passes through the grating 3 against the monochromatic light source 1.

[0027] S4: Keep the position of the laser 4 and place a light shielding screen 6 on the side of the light screen 2 close to the observer 5.

[0028] S5: Obtain the distance x between the grating 3 and the light screen 2 and the distance Y between the first-order or second-order diffraction stripes (specifically, the distance between the positive and negative stripes of the corresponding order) of the laser 4 on the light shielding screen 6.

[0029] S6: Calculate the wavelength or grating constant according to formula I. In this step, if the grating constant needs to be detected, a monochromatic light source 1 with a known wavelength is used; if the wavelength needs to be detected, a grating 3 with a known grating constant is used.

[0030] (I) in, is the diffraction angle, is the wavelength, k is 1 or 2, d is the grating constant, , y=Y / 2.

[0031] Preferably, in step S5, the distance between the first-order diffraction fringes of the laser 4 on the light shielding screen 6 is obtained, that is, k is 1, then in step S5, calculation is performed according to formula II: (II).

[0032] S7: Adjust the distance between the grating 3 and the light screen 2 to perform multiple detections (correspondingly adjust the width of the slit, the position of the observer 5 and the position of the laser 4), and calculate the average value of the multiple detections.

[0033] Example 4 Embodiment 4 provides a wavelength detection method, the method comprising the following steps: S1: construct an optical path as described in Example 1; wherein the monochromatic light source 1 is a low-pressure sodium monochromatic light source, the distance between the light screen 2 and the grating 3 is 10-20 cm, and the grating constant of the grating 3 is d=1 / 300 mm.

[0034] S2: Adjust the width of the slit of the light screen 2 so that the observer 5 can observe the diffraction fringes on the light screen 2, and adjust the position of the observer 5 in the direction of the optical axis so that the zero-order diffraction fringes observed by the observer 5 after the transmitted light of the monochromatic light source 1 passing through the grating 3 are aligned with the slit.

[0035] S3: Turn on the laser 4, and adjust the position of the laser 4 in the direction of the optical axis so that the real image of the first-order diffraction stripes of the laser passing through the grating 3 coincides with the virtual image of the first-order diffraction stripes observed by the observer 5 after the transmitted light of the laser passing through the grating 3 against the monochromatic light source 1. At this time, the distance between the positive and negative first-order diffraction stripes of the laser after passing through the grating 3 is equal to the distance between the positive and negative first-order diffraction stripes of the virtual image of the diffraction stripes of the monochromatic light observed by the eyes.

[0036] S4: Keep the position of the laser 4 and place a white paper on the side of the light screen 2 close to the observer 5.

[0037] S5: Obtain the distance x between the grating 3 and the light screen 2 and the distance 2y between the first-order diffraction fringes of the laser 4 on the white paper.

[0038] S6: Calculate the wavelength according to formula II.

[0039] (II).

[0040] S7: adjusting the distance between the grating 3 and the light screen 2 to detect the wavelength multiple times, and calculating the average value of the wavelengths detected multiple times.

[0041] Example 5 Example 5 provides a wavelength detection method, the process of which is consistent with that of Example 4, and the average value is calculated after six detections, and the results are shown in Table 2. The wavelength is measured by a spectrometer, which is a JJY type spectrometer, and the operation process is conventional technology, and detailed description is omitted in this embodiment. The results are shown in Table 1.

[0042] Table 1

[0043] According to the data in Table 1, the wavelength of the sodium lamp is calculated to be: λ=586.949±0.198nm.

[0044] The measurement results using the method of this patent are shown in Table 2: Table 2

[0045] According to the data in Table 2, the wavelength of the sodium lamp is calculated to be: λ=588.751±0.104nm.

[0046] Analysis of measurement results: The experimental data measured by the spectrometer platform are shown in Table 1, the average wavelength of the sodium lamp is 586.949nm, and the standard error is 0.198nm; the measured data of the sodium lamp wavelength measured by the method of this patent are shown in Table 2, the average wavelength of the sodium lamp is 588.751nm, and the standard error is 0.104nm. The recognized value of the average wavelength of the second yellow line of the low-pressure sodium lamp is 589.3nm. Obviously, the measured value of the sodium lamp wavelength measured by the method of the present invention is closer to the actual value, that is, the wavelength measured by the device and method of the present invention is accurate.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical detection method, characterized in that: The method comprises the following steps: S1: build the optical path; S2: adjusting the width of the slit of the light screen (2) so that the observer (5) can observe the diffraction fringes on the light screen (2), and adjusting the position of the observer (5) in the direction of the optical axis so that the observer (5) can align the zero-order diffraction fringes observed by the observer (5) against the transmission light of the monochromatic light source (1) after passing through the grating (3) with the slit; S3: Turn on the laser (4), and adjust the position of the laser (4) in the direction of the optical axis so that the real image of the diffraction stripes of the laser passing through the grating (3) coincides with the virtual image of the diffraction stripes observed by the observer (5) when the light transmitted through the grating (3) against the monochromatic light source (1); S4: Keep the laser (4) in position and place a light shielding screen (6) on the side of the light screen (2) close to the observer (5); S5: Obtaining the distance x between the grating (3) and the light screen (2) and the distance Y between the first-order or second-order diffraction fringes of the laser (4) on the light shielding screen (6); S6: Calculate the wavelength or grating constant based on x and Y using the Fraunhofer diffraction law; The optical path comprises a monochromatic light source (1), a light screen (2), a grating (3) and a laser (4); the light screen (2) is provided with a slit with adjustable width; the monochromatic light source (1), the light screen (2), the grating (3) and the laser (4) are arranged in sequence along the optical axis; the light screen (2) and the grating (3) are both perpendicular to the optical axis; an observer (5) is located on a side of the grating (3) away from the light screen (2); the monochromatic light source (1), the slit, the grating (3) and the laser (4) are at the same height; and the laser of the laser (4) is parallel to the optical axis.

2. The optical detection method according to claim 1, characterized in that: If it is necessary to detect the grating constant, a monochromatic light source (1) with a known wavelength is used; if it is necessary to detect the wavelength, a grating (3) with a known grating constant is used.

3. The optical detection method according to claim 1, characterized in that: In step S6, calculation is performed according to formula I: (I) in, is the diffraction angle, is the wavelength, k is 1 or 2, d is the grating constant, , y=Y / 2.

4. The optical detection method according to claim 3, characterized in that: In step S5, the distance between the first-order diffraction fringes of the laser (4) on the light shield (6) is obtained, and then in step S6, the calculation is performed according to formula II: (II)。 5. The optical detection method according to claim 1, characterized in that: The method further comprises: adjusting the distance between the grating (3) and the light screen (2) to perform multiple detections, and calculating an average value of the multiple detections.

6. The optical detection method according to claim 1, characterized in that: When conducting a wavelength teaching and testing experiment, the monochromatic light source (1) is a low-pressure sodium monochromatic light source, and x is 10-20 cm.

7. An optical detection device, characterized in that: The invention comprises a monochromatic light source (1), a light screen (2), a grating (3), a laser (4), a light shielding screen (6) and a distance detection tool, wherein the light screen (2) is provided with a slit with adjustable width, the monochromatic light source (1), the light screen (2), the grating (3) and the laser (4) are arranged in sequence along the optical axis, the light screen (2) and the grating (3) are perpendicular to the optical axis, an observer (5) is located on the side of the grating (3) away from the light screen (2), the monochromatic light source (1), the slit, the grating (3) and the laser (4) are at the same height, the laser of the laser (4) is parallel to the optical axis, and the light shielding screen (6) can shield the light screen (2); The light screen (2), grating (3) and laser (4) can be adjusted in the direction of the optical axis; The width of the slit allows an observer (5) to observe diffraction fringes on the light screen (2); The distance between the observer (5) and the grating (3) enables the observer (5) to align the zero-order diffraction fringe observed by the observer (5) against the transmission light of the monochromatic light source (1) after passing through the grating (3) with the slit; The distance between the laser (4) and the grating (3) allows the real image of the diffraction fringes of the laser light passing through the grating (3) to coincide with the virtual image of the diffraction fringes observed by an observer (5) when the light transmitted through the grating (3) against the monochromatic light source (1) is aligned; During detection, the light shielding screen (6) is placed on the side of the light screen (2) close to the observer (5); The distance detection tool is used to detect the distance between the light screen (2) and the grating (3) and the distance between the first-order or second-order diffraction stripes of the laser (4) on the light shielding screen (6).

8. The optical detection device according to claim 7, characterized in that: The monochromatic light source (1), the light screen (2), the grating (3) and the laser (4) are all arranged on an optical bench platform, and the position parameters of the light screen (2) and the grating (3) can be read on the optical bench platform to obtain the distance between the light screen (2) and the grating (3); the distance detection tool is a vernier caliper for obtaining the distance between the first-order or second-order diffraction fringes of the laser (4) on the light shielding screen (6), and the light shielding screen (6) is white paper.

9. A light experiment teaching tool, characterized in that: Comprising the optical detection device as claimed in claim 7, for detecting wavelength.

10. The optical experiment teaching tool according to claim 9, characterized in that: The monochromatic light source (1) is a low-pressure sodium monochromatic light source, the distance between the light screen (2) and the grating (3) is 10-20 cm, and the grating constant d of the grating (3) is 1 / 300 mm.

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