Liquid acoustic propagation of density wave visualization experimental device and experimental method

Abstract

A liquid sound propagation density wave visualization experiment device and experiment method, the base is equipped with sound propagation experiment groove and optical assembly, one long side wall and two wide side walls of sound propagation experiment groove are rectangular flat plate structure, the position of the other long side wall is provided with three prism, three side faces of three prism are sound propagation experiment groove side wall face, light incidence face, light spot presentation face respectively, image display layer is arranged on light spot presentation face, the center of one wide side wall of sound propagation experiment groove is provided with ultrasonic transducer; Optical assembly is that laser is arranged on first support, and Frensel lens is arranged on second support, and Frensel lens is located on the light emission direction of laser, laser emitted by laser is changed into parallel laser beam through Frensel lens, enters from the incidence face of three prism, and after reflection on the wall face of sound propagation experiment groove, light spot is presented on light spot presentation face.The present application can make students see the propagation characteristics of sound wave in liquid directly and clearly in the teaching process, and significantly improve the teaching efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of university physics experimental instruments, and particularly relates to a sound wave propagation visualization demonstration experiment device and a demonstration experiment method. BACKGROUND

[0002] It is known that a sound wave is a longitudinal wave, but the sound wave is invisible. In order to demonstrate the propagation characteristics of the sound wave to students, a low-frequency vibration source connected to one end of a spring is generally used to form a periodic change of pitch between the sparse and dense phases on the spring, to demonstrate the longitudinal wave propagation image of the sound wave in a solid medium, to demonstrate the longitudinal wave propagation image of the sound wave in a gaseous medium by using a Kundt tube, and to have a very good demonstration effect. When the sound wave propagates in a liquid, it is theoretically considered that the density of the liquid will form a periodic change between the sparse and dense phases in time and space, and therefore is called a sparse-dense wave. However, the sparse-dense wave is invisible. Although the important content of the university physics experiment, i.e., the ultrasonic grating, indirectly reflects that the density of water appears a periodic change between the sparse and dense phases in space due to the ultrasonic standing wave, but it is not directly or indirectly observed in the water, but is obtained by inversely deducing the diffraction fringes of the transmitted light by the ultrasonic grating, and the diffraction fringes of the ultrasonic grating generally need to be observed by a micrometer eyepiece, and cannot be seen by the naked eye, which cannot meet the requirements of the demonstration experiment. At the same time, the ultrasonic grating is a transmission diffraction phenomenon of light, and can only show the acousto-optic effect in a transparent liquid, and cannot directly or indirectly observe the phenomenon that the density of the sparse-dense phase appears a periodic change due to the ultrasonic standing wave in a non-transparent liquid. Obviously, the students cannot intuitively feel the corresponding relationship between the nodes or antinodes of the ultrasonic standing wave in the liquid and the "sparse" or "dense" of the density of the liquid by the ultrasonic grating, and cannot meet the needs of the students to intuitively explore the propagation characteristics of the sound wave in the liquid. Therefore, it is of great significance to develop a visualization experiment device of the sparse-dense wave of the sound propagation in a transparent liquid and a non-transparent liquid for the students to deeply understand the propagation characteristics of the sound wave in the liquid and to popularize the related knowledge to the public. SUMMARY

[0003] The technical problem to be solved by the application is to provide a visualization experiment device of the sparse-dense wave of the sound propagation in a liquid, which has a simple structure, is convenient to operate, and improves the teaching efficiency.

[0004] The technical scheme adopted to solve the above technical problems is: a liquid sound propagation sparse and dense wave visualization experiment device, a sound propagation experiment tank and an optical assembly are arranged on a base, the sound propagation experiment tank is a cuboid, one long side wall and two wide side walls of the sound propagation experiment tank are rectangular plate structures, a triangular prism is arranged at the position of the other long side wall, three side surfaces of the triangular prism are respectively a sound propagation experiment tank side wall surface, a light incidence surface and a light spot presenting surface, an image display layer is arranged on the light spot presenting surface, and an ultrasonic transducer is arranged at the center of one wide side wall of the sound propagation experiment tank; the optical assembly is provided with a laser on a first support and a Fresnel lens on a second support, the Fresnel lens is located on the light emission direction of the laser, the laser emitted by the laser is changed into a parallel laser beam by the Fresnel lens, enters the triangular prism from the incidence surface of the triangular prism, and is obliquely incident on the sound propagation experiment tank side wall surface of the triangular prism, and the reflected light presents an optical image on the image display layer of the light spot presenting surface.

[0005] As a preferred technical scheme, the cross section of the triangular prism is a right triangle, the side of the right triangle is the sound propagation experiment tank side wall surface, the short right angle side of the right triangle is the light incidence surface, and the long right angle side of the right triangle is the light spot presenting surface, and the included angle β between the light spot presenting surface and the sound propagation experiment tank side wall surface of the triangular prism is 20°-35°.

[0006] As a preferred technical scheme, the light incidence surface is covered with a light shielding layer, and a rectangular light incidence window is arranged on the light shielding layer.

[0007] As a preferred technical scheme, the laser is provided with a beam expander.

[0008] As a preferred technical scheme, the inner side of the side wall where the ultrasonic transducer of the sound propagation experiment tank is located is provided with a sound absorbing layer.

[0009] As a preferred technical scheme, the image display layer arranged on the light spot presenting surface is a white paint layer.

[0010] An experimental method of a liquid sound propagation sparse and dense wave visualization experiment device, which is composed of the following steps:

[0011] Step 1. Fill the sound propagation experiment tank with liquid, turn on the laser, and adjust the position of the first support or the second support so that the light outlet of the laser is located at the focal point of the Fresnel lens.

[0012] Step 2. The parallel laser beams output by the Fresnel lens enter the three-prism through the rectangular light incident window on the light shielding layer, and form refraction and reflection on the interface between the three-prism and the liquid in the sound propagation experiment tank. The reflection and refraction of the laser beams on the interface between the three-prism and the liquid are observed from above the three-prism. The first support and the second support are adjusted synchronously to change the incident angle of the laser beams on the interface between the three-prism and the liquid, so that the laser beams are totally reflected on the interface between the three-prism and the liquid. At this time, the light spot of the three-prism presents the image on the image display layer on the surface, and a rectangular light spot with uniform brightness is displayed on the image display layer.

[0013] Step 3. The ultrasonic transducer is turned on, the frequency of the power supply of the ultrasonic transducer is adjusted, and the change of the optical image on the image display layer on the light spot presenting surface of the three-prism is observed at the same time. When the ultrasonic standing wave is formed in the liquid in the sound propagation experiment tank, the density of the liquid in the sound propagation experiment tank forms a periodic change between the sparse and dense phases. Correspondingly, the optical image with the interlaced brightness between the strong and weak areas is formed on the image display layer on the light spot presenting surface of the three-prism. The area with high brightness corresponds to the node area of the sparse and dense waves formed by the ultrasonic standing wave in the sound propagation experiment tank, and the area with relatively low brightness corresponds to the antinode area of the sparse and dense waves formed by the ultrasonic standing wave in the sound propagation experiment tank. In this way, the visualization of the propagation of the sparse and dense waves of the sound wave in the liquid is realized.

[0014] The beneficial effects of the present application are as follows:

[0015] The long side wall of the sound propagation experiment tank in the present application is a three-prism. When the ultrasonic standing wave is formed in the liquid in the sound propagation experiment tank, the density of the water presents a periodic distribution between the sparse and dense phases. Correspondingly, the reflected laser beams of the three-prism and the liquid interface project on the light spot presenting surface of the three-prism to form the optical image with the interlaced brightness between the strong and weak areas. In this way, the visualization of the propagation of the sparse and dense waves of the sound wave in the liquid is realized. At the same time, the reflected light reflecting the density change information of the liquid does not enter the liquid, that is, the transparency of the liquid does not affect the experimental results. Therefore, the present application not only can directly demonstrate the sparse and dense waves formed by the ultrasonic standing wave in the transparent liquid, but also can realize the visualization of the sparse and dense waves formed by the ultrasonic standing wave in the opaque liquid.

[0016] The present application has the advantages of simple structure, convenient operation, and the like. The students can directly and clearly see the propagation characteristics of the sound wave in the liquid, and the teaching efficiency is significantly improved. The present application can also be used for popular science display in science and technology museums. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a structural schematic view of the liquid sound propagation sparse and dense wave visualization experiment device in the present application.

[0018] Figure 2 FIG. 2 is a top view of the liquid sound propagation sparse and dense wave visualization experiment device in the present application.

[0019] Figure 3This is a schematic diagram illustrating the experimental principle of the present invention.

[0020] Figure 4 This is an optical image formed by ultrasonic standing waves in a liquid according to the present invention.

[0021] The components include: base 1, second support 2, first support 3, laser 4, Fresnel lens 5, sound propagation experimental tank 6, prism 61, light spot presentation surface 611, side wall surface of sound propagation experimental tank 612, light incident surface 613, sound absorbing layer 7, and light shielding layer 8. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0023] exist Figure 1 , 2 In this embodiment, the visualization experimental device for sound propagation compression waves in a liquid includes a base 1, a sound propagation experimental tank 6, and optical components. The sound propagation experimental tank 6 is rectangular and contains liquid. The rear long sidewall and two wide sidewalls of the sound propagation experimental tank 6 are rectangular flat plates. A prism 61 is positioned on the front long sidewall. The cross-section of the prism 61 is a right triangle. The hypotenuse of the right triangle forms the sidewall surface 612 of the sound propagation experimental tank, and the short right-angled side forms the light incident surface 613. A light-shielding layer 8 covers the light incident surface 613, and a rectangular light-shielding opening is formed on the light-shielding layer 8. The light-emitting window has a long right-angled triangle face 611, which is the light spot display surface. A white paint layer is sprayed on the light spot display surface 611 as an image display layer. The angle between the light spot display surface 611 of the prism 61 and the side wall 612 of the sound propagation experimental tank is 20° to 35°. A foam-like sound-absorbing layer 7 is provided on the inner side of the left wide side wall of the sound propagation experimental tank 6, and an ultrasonic transducer is installed in the center. The ultrasonic transducer is used to form an ultrasonic standing wave in the liquid in the sound propagation experimental tank 6.

[0024] The optical components include a first support 3, a second support 2, a laser 4, and a Fresnel lens 5. The laser 4 is mounted on the first support 3, and the Fresnel lens 5 is mounted on the second support 2. The Fresnel lens 5 is located in the direction of the laser 4's light emission. The laser emitted by the laser 4 is transformed into a parallel laser beam by the Fresnel lens 5, which enters through the rectangular light incident window on the light-shielding layer 8 on the incident surface 613 of the prism 61 and obliquely strikes the side wall 612 of the acoustic propagation experimental tank of the prism 61. The reflected light presents a rectangular optical image on the image display layer on the light spot presentation surface 611.

[0025] The experimental setup for visualizing the compression and rarefaction waves of sound propagation in a liquid in this embodiment consists of the following steps:

[0026] Step 1. Fill the liquid in the sound propagation experimental tank 6, turn on the laser 4, and adjust the position of the first support 3 or the second support 2 so that the light outlet of the laser 4 is located at the focal point of the Fresnel lens 5;

[0027] Step 2. The parallel laser beam output by the Fresnel lens 5 enters the three-prism 61 through the rectangular light inlet window on the light shielding layer 8, and forms refraction and reflection on the interface between the three-prism 61 and the liquid in the sound propagation experimental tank 6. From the top of the three-prism 61, the reflection and refraction of the laser beam on the interface between the three-prism 61 and the liquid are observed, and the first support 3 and the second support 2 are adjusted synchronously to change the incident angle of the laser beam on the interface between the three-prism 61 and the liquid, so that the laser beam is just totally reflected on the interface between the three-prism 61 and the liquid. At this time, the light spot of the three-prism 61 presents a rectangular light spot with uniform brightness on the image display layer on the surface 611.

[0028] Step 3. Turn on the ultrasonic transducer, adjust the frequency of the ultrasonic transducer power supply, and at the same time observe the changes of the optical image on the image display layer on the light spot presenting surface 611 of the three-prism 61, such as Figure 3 When the ultrasonic standing wave is formed in the liquid in the sound propagation experimental tank 6, the density of the liquid is the smallest at the node of the ultrasonic standing wave, and the density of the liquid is the largest at the antinode of the ultrasonic standing wave. The density of the liquid gradually increases from the node to the antinode, and the density of the liquid gradually decreases from the antinode to the node. The region where the density of the liquid decreases, i.e. the region near the node, has a smaller refractive index than the refractive index of the liquid without the action of the ultrasonic wave. The light incident on this region is totally reflected at the interface between the three-prism 61 and the liquid, and the intensity of the light reflected onto the image display layer on the light spot presenting surface 611 of the three-prism 61 does not change. The region where the density of the liquid increases, i.e. the region near the antinode, has a larger refractive index than the refractive index of the liquid without the action of the ultrasonic wave. In this case, the laser beam cannot be totally reflected at the interface between the three-prism 61 and the liquid, i.e. the refracted light appears in the liquid in this region. Accordingly, the intensity of the light reflected onto the image display layer on the light spot presenting surface 611 of the three-prism 61 at the interface between the three-prism 61 and the liquid in this region is weakened. Finally, the sparse-dense wave formed by the ultrasonic standing wave in the experimental tank forms a stable and bright optical image with alternating brightness on the image display layer on the light spot presenting surface 611 of the three-prism 61, as shown in Figure 4 The region with high brightness corresponds to the node region of the sparse-dense wave formed by the ultrasonic standing wave in the sound propagation experimental tank 6, and the region with relatively low brightness corresponds to the antinode region of the sparse-dense wave formed by the ultrasonic standing wave in the sound propagation experimental tank 6. In this way, the visualization of the propagation of the sparse-dense wave of the sound wave in the liquid is realized.

[0029] The liquid in the embodiment can be a transparent liquid, such as water, or an opaque liquid, such as a liquid with ink added to water.

Claims

1. An experimental method of a liquid in sound propagation density wave visualization experimental device, characterized in that, The experimental device is that the base (1) is provided with a sound propagation experiment tank (6) and an optical assembly, the sound propagation experiment tank (6) is a cuboid, one long side wall and two wide side walls of the sound propagation experiment tank (6) are rectangular plate structures, and the other long side wall is provided with a triangular prism (61); three side faces of the triangular prism (61) are a sound propagation experiment tank side wall (612), a light incidence face (613) and a light spot presenting face (611) respectively; the light spot presenting face (611) is provided with an image display layer; and one wide side wall of the sound propagation experiment tank (6) is provided with an ultrasonic transducer; the optical assembly is that a laser (4) is arranged on a first support (3), and a Fresnel lens (5) is arranged on a second support (2); the Fresnel lens (5) is located on a light emission direction of the laser (4); the laser emitted by the laser (4) becomes a parallel laser beam through the Fresnel lens (5), enters the incidence face (613) of the triangular prism (61), and is obliquely incident on the sound propagation experiment tank side wall (612) of the triangular prism (61); and the reflected light presents an optical image on the image display layer of the light spot presenting face (611); The experimental method comprises the following steps: Step 1, filling the sound propagation experiment tank (6) with liquid, turning on the laser (4), adjusting the positions of the first support (3) or the second support (2) so that the light outlet of the laser (4) is located at the focal point of the Fresnel lens (5); Step 2, the parallel laser beam output by the Fresnel lens (5) enters the triangular prism (61) through a rectangular light incidence window on a light shielding layer (8), forms refraction and reflection on the interface between the triangular prism (61) and the liquid in the sound propagation experiment tank (6), the reflection and refraction of the laser beam on the interface between the triangular prism (61) and the liquid are observed from above the triangular prism (61), the first support (3) and the second support (2) are adjusted synchronously, the incidence angle of the laser beam on the interface between the triangular prism (61) and the liquid is changed, and the laser beam is just totally reflected on the interface between the triangular prism (61) and the liquid; at this time, a rectangular light spot with uniform brightness is displayed on the image display layer on the light spot presenting face (611) of the triangular prism (61); Step 3, turning on the ultrasonic transducer, adjusting the frequency of the power supply of the ultrasonic transducer, and observing the change of the optical image on the image display layer on the light spot presenting face (611) of the triangular prism (61) at the same time; when the ultrasonic standing wave is formed in the liquid in the sound propagation experiment tank (6), the density of the liquid in the ultrasonic standing wave in the sound propagation experiment tank (6) forms periodic changes between the sparse and dense phases; correspondingly, the optical image with the interphase between the brightness and the weak brightness is formed on the image display layer on the light spot presenting face (611) of the triangular prism (61); the area with high brightness corresponds to the node area of the sparse and dense waves formed by the ultrasonic standing wave in the sound propagation experiment tank (6); and the area with relatively low brightness corresponds to the antinode area of the sparse and dense waves formed by the ultrasonic standing wave in the sound propagation experiment tank (6); thus, the visualization of the propagation of the sound wave in the liquid is realized.

2. The experimental method of the liquid acoustic propagation visualization device according to claim 1, characterized in that: The cross section of the triangular prism (61) is a right triangle, the hypotenuse of the right triangle is the sound propagation experiment tank side wall (612), the short right angle of the right triangle is the light incidence surface (613), the long right angle of the right triangle is the light spot presenting surface (611), the included angle β between the light spot presenting surface (611) of the triangular prism (61) and the sound propagation experiment tank side wall (612) is 20°-35°.

3. The experimental method of the liquid acoustic visualization device according to claim 1 or 2, characterized in that: The light incidence surface (613) is covered with a light shielding layer (8), and a rectangular light incidence window is formed in the light shielding layer (8).

4. The experimental method of the liquid acoustic propagation visualization device according to claim 1, characterized in that: An expander is arranged on the laser (4).

5. The experimental method of the liquid acoustic propagation visualization experimental device according to claim 1, characterized in that: An acoustic absorption layer (7) is arranged on the inner side of the side wall of the sound propagation experiment tank (6) where the ultrasonic transducer is located.

6. The experimental method of the liquid acoustic propagation visualization experimental device according to claim 1, characterized in that: The image display layer arranged on the light spot presenting surface (611) is a white paint layer.

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