CN107545817B - A kind of equal thickness interference apparatus for demonstrating and demenstration method - Google Patents

Abstract

The invention relates to a demonstration device and demonstration method of equal thickness interference. The device comprises a container with a circular opening at the top, and when the circular opening is sealed with a soap film, the pressure inside the container can be adjusted, and when the pressure inside the container changes, the The shape of the soap film is changed; the equal-thickness interference demonstration device and demonstration method provided by the present invention can not only display the interference pattern of Newton's ring, but also display the interference pattern of wedge. In addition, the device can not only display the interference pattern of equal thickness with thin center and thick periphery, but also display the interference pattern of equal thickness with thick center and thin edge.

Description

An equal-thickness interference demonstration device and demonstration method

technical field

The invention relates to the field of physical experiment instruments, in particular to an equal-thickness interference demonstration device and a demonstration method.

Background technique

Thin-film interference is divided into two types, one is called equal-tilt interference, and the other is called equal-thickness interference. Equal-thickness interference is the interference fringes formed near the film when parallel light is incident on the film. Where the thickness of the film is the same, interference fringes with the same brightness are formed, so it is called equal thickness interference.

Both Newton's ring and wedge-shaped plate interference belong to equal-thickness interference. It plays a great role in production and life practice, such as measuring the wavelength of light, accurately measuring the length, thickness and angle of tiny objects, detecting the surface finish and flatness of workpieces, and the internal stress distribution of mechanical parts, etc. It can be seen that equal-thickness interference plays an important role in university optics courses. It is of great significance to let students better understand the phenomenon of equal-thickness interference while learning theoretical knowledge.

The Newton ring device is usually composed of a plane made of optical glass and a spherical surface with a large radius of curvature, forming a wedge-shaped thin layer of air between the two surfaces. Taking a convex surface as an example, when monochromatic light is incident vertically, the incident light is reflected sequentially on the upper and lower surfaces of the air thin layer, and interference occurs when it meets the lens surface. Where the thickness of the air film is the same, the interference fringes are the same. This kind of interference is called equal-thickness interference. The interference fringes are a series of concentric rings with alternating light and dark centered on the contact point, called Newton's rings.

At present, the equal-thickness interference instrument used in the laboratory is mainly composed of a reading microscope and a Newton ring device. At present, the experimental method of most schools is to observe the Newton ring phenomenon through a reading microscope. Students observe in the microscope, record the number of fringes in the field of view, and then read The readings of the scale on the equal-thickness interferometer are hand-written, and the submitted experimental reports are based on the hand-written experimental data. The traditional equal-thickness interferometer not only has a large observation volume, but also takes a long time to prepare for the experiment, and it is quite difficult to observe, and it is extremely prone to errors.

Contents of the invention

Aiming at the problems that the above-mentioned existing equal-thickness interferometer not only has a large observation volume, but also takes a long time to prepare for the experiment, and is quite difficult to observe and is very prone to errors, the present invention provides an equal-thickness interference demonstration device and demonstration method.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

An equal-thickness interference demonstration device, which includes a container with a circular opening at the top, and when the circular opening is sealed with a soap film, the pressure in the container can be adjusted, and when the pressure in the container changes, the shape of the soap film can be changed. Change.

The container is made of elastic material.

The container is a squeeze-deformable plastic bottle.

A pressure regulating port is provided at the bottom of the side wall of the container.

The container is a transparent container.

A demonstration method using the equal-thickness interference demonstration device as described above, comprising the following steps:

Step 1: Immerse the top of the device in the soap solution, and then take it out. At this time, a layer of soap film will be formed on the edge of the top port of the container;

Step 2: Reduce the gas pressure in the container by adjusting, resulting in a concave shape of the soap film; at this time, the Newton ring pattern can be observed from the reflected light of the soap film, the outermost circle is a dark stripe, and the center is a bright or dark spot;

Step 3: By adjusting and increasing the gas pressure in the container, the soap film rises to make the soap film flat, and then tilt the device. At this time, the wedge pattern can be observed from the reflected light of the soap film, which is equidistant interference fringes;

Step 4: Return the device to the state before tilting, continue to increase the gas pressure in the container through adjustment, and the soap film rises, resulting in a convex shape of the soap film; at this time, the Newton ring pattern can be observed from the reflected light of the soap film. It is a dark spot, and the outermost circle is a dark or light stripe.

Beneficial effects of the present invention:

The equal-thickness interference demonstration device and demonstration method provided by the present invention can not only display the interference pattern of the Newton ring, but also display the interference pattern of the wedge. In addition, this device can not only display equal-thickness interference patterns with thin center and thick periphery, but also display equal-thickness interference patterns with thick center and thin edges;

The overall weight of the present invention is light, can be carried around for demonstration, and occupies little space. The invention can quickly carry out experiments, and has very obvious phenomena at the same time, which is convenient for demonstrating equal-thickness interference phenomena in teaching and popularizing physical knowledge. At the same time, because there is no use of high-cost optical equipment such as optical microscopes and flat laser beams, and only low-cost ordinary optical components are used to complete the experiment, it has stronger market competitiveness against other equal-thickness interferometric instruments. The invention has the advantages of convenient portability, simple and convenient operation, low cost, good observation effect, wide application range, convenient teaching demonstration and the like.

Description of drawings

Fig. 1 is a schematic diagram of the device structure of the present invention;

Fig. 2 is the structural principle diagram two of the device of the present invention;

Fig. 3 is the structural schematic drawing three of the device of the present invention;

Fig. 4 is the interference pattern of Newton's ring in Fig. 1;

Figure 5 is the interference pattern of the wedge in Figure 2;

Fig. 6 is the interference pattern of Newton's ring in Fig. 3;

Reference signs: 1, container, 2, pressure regulating port, 3, Newton ring, 4, wedge.

Detailed ways

The present invention will be further elaborated below in combination with specific embodiments.

As shown in the figure: an equal thickness interference demonstration device, the device includes a container 1 with a circular opening at the top, the container 1 is in the shape of an inverted funnel, and the bottom of the side wall of the container 1 is provided with a pressure regulating port 2. When the circular opening of 1 is sealed with a soap film, the pressure in the container 1 can be adjusted by inflating or deflating the pressure regulating port 2, and when the pressure in the container changes, the shape of the soap film can be changed.

A demonstration method utilizing the equal-thickness interference demonstration device described above comprises the following steps:

Step 1: Immerse the top of the device in the soap solution, and then take it out. At this time, a layer of soap film will be formed on the edge of the top port of the container;

Step 2: Reduce the gas pressure in the container by adjusting, so that the soap film is in a concave shape; at this time, the Newton ring pattern in Figure 4 can be observed from the reflected light of the soap film, the outermost circle is dark stripes, and the center is bright spots or dark spots;

Step 3: By adjusting and increasing the gas pressure in the container, the soap film rises to make the soap film flat, and then tilt the device. At this time, the wedge pattern in Figure 5 can be observed from the reflected light of the soap film, which is equal to Spacing interference fringes;

Step 4: Return the device to the state before tilting, and continue to increase the gas pressure in the container through adjustment, so that the soap film rises, causing the soap film to be convex; at this time, it can be observed from the reflected light of the soap film as shown in Figure 6 Newton's ring pattern, with a dark spot in the center and dark or light stripes in the outermost circle.

Traditional equal-thickness interference devices are divided into Newton rings and wedges, both of which are made of hard transparent materials such as glass. The device can display not only the interference pattern of Newton's ring, but also the interference pattern of wedge. In addition, the device can not only display the interference pattern of equal thickness with thin center and thick periphery, but also display the interference pattern of equal thickness with thick center and thin edge.

Claims (5)

1. a kind of demenstration method using equal thickness interference apparatus for demonstrating, the equal thickness interference apparatus for demonstrating includes that top is equipped with circle Open container (1), and when circular open is sealed with soap film, container inner pressure can be adjusted, when container inner pressure changes, The shape of soap film can be made to change, which comprises the following steps:

Step 1: the top of device is immersed in soap solution, is then taken out, at this point, one can be formed at container head opening's edge Layer soap film；

Step 2: reduce gas in container pressure by adjusting, cause soap film in concave；It at this time can be from soap film Newton's ring pattern is observed in reflected light, outmost turns are dark fringe, and center is speck or blackening；

Step 3: increasing gas in container pressure by adjusting, and soap film increases, and so that soap film is become plane, then inclination dress It sets, can observe splitter pattern from the reflected light of soap film at this time, be equidistant interference fringe；

Step 4: restoring the state before inclination for device, continues to increase gas in container pressure by adjusting, and soap film increases, Cause soap film in convex shape；Newton's ring pattern can be observed from the reflected light of soap film at this time, center is blackening, most Outer ring is dark fringe or bright rays.

2. utilizing the demenstration method of equal thickness interference apparatus for demonstrating as described in claim 1, it is characterised in that: the container (1) It is made of elastic material.

3. utilizing the demenstration method of equal thickness interference apparatus for demonstrating as described in claim 1, it is characterised in that: the container (1) For the plastic bottle of extrudable deformation.

4. utilizing the demenstration method of equal thickness interference apparatus for demonstrating as described in claim 1, it is characterised in that: the container (1) The bottom of side wall is equipped with pressure modulating opening (2).

5. utilizing the demenstration method of equal thickness interference apparatus for demonstrating as described in claim 1, it is characterised in that: the container (1) For transparent vessel.