23 9 Junior High School Physics Are the following statements about the phenomenon of light correct

Solution: According to the total reflection condition of light, light enters the photophobic medium from the optically dense medium, and the incident angle is greater than or equal to the critical angle; It can be determined by the refraction of light; There will be a bright spot in the center of the shadow on the light screen, which is a diffraction phenomenon of light; This is due to the fact that the refractive index cluster of the upper air of the desert is not larger than that of the lower air

a. From the total reflection of light, it can be seen that the refractive index of the inner core material of the optical fiber filament is larger than that of the outer material, so the state god A is correct;

b. From the phenomenon of light refraction, it can be seen that the image of the object seen will be higher than the actual position of the object, so b is correct;

c. There will be a bright spot in the center of the shadow on the light screen, which is the diffraction phenomenon of light, so C is correct;

d. The reason is that the refractive index of the upper and upper air of the desert is larger than that of the lower air, and the light is fully reflected, so D is wrong;

If you choose the wrong question for this question, you should choose: d

4. The following statements about the phenomenon of light are incorrect ( ).

a The refractive index of the core material of the optical fiber filament is larger than that of the jacket material.

b When a diver in the water obliquely looks at an object on the shore, the image of the object will be higher than the actual position of the object.

c When a laser is irradiated vertically on a small opaque plate, a bright spot will appear in the center of the shadow on the light screen, which is a diffraction phenomenon of light.

d The cause of desert mirage is that the refractive index of the upper and upper layers of the desert is smaller than that of the lower air, and the total reflection of light occurs.

Solution: a. Light shoots from the air to the water surface, and the reflection occurs on the water surface, making the water waves look sparkling; B, the light outside the cab at night is relatively dark, if you turn on the lights in the cab, the light of the indoor object is relatively strong, you can form a virtual image (plane mirror imaging) in front of the car through the front windshield, interfere with the driver's line of sight; c. When people look in the mirror, they always look close to the mirror, and the reason is that the plane mirror feels larger when they are close, which is a problem of perspective; d. The immediate effect is a shadow, and the mirage is formed by the deflation of light when it propagates in a medium with the same uneven density

a. Under the sun, the river surface blown by the breeze is sparkling, which is due to the reflection of light on the river surface and the shape of the mountain, so this option is correct

B, when driving at night, if you turn on the electric light of the cab, the indoor object will be imaged on the cab glass, and the outside object can not be seen clearly, so this option is wrong

c. When people look in the mirror, they always look close to the mirror, the reason is that when they get closer, they feel that the image has become bigger, but the size of the image has not changed, but the perspective has become larger, which is a feeling, not a fact; Therefore, this option is incorrect

d. The immediate effect is a shadow, which is a phenomenon of linear propagation of light; Mirage is the result of light rays being refracted in a straight line due to the different air densities, so this option is incorrect

Therefore, choose a 2, and among the following phenomena related to light, the correct statement is ( ).

a The sunshine and the sparkling surface of the river with a breeze are reflected in light.

b When the car is driving at night, the electric lights in the cab should be turned on to ensure driving safety.

c When a person looks in the mirror, the beam is always close to the mirror, and the reason is that the image of the flat mirror becomes larger when it is close.

d Immediate and mirages are phenomena that are formed by the linear propagation of light.

Answer aa, the statement is correct, seeing the light on the water is due to the reflection of the light into the human eye; b. The statement is wrong, if the light is emitted on the plane mirror at an angle of 30° to the mirror, the reflection angle is also 60°; c. The statement is wrong, when people look in the mirror, they always look close to the mirror, the reason is that when they get closer, they feel like they get bigger, but the size of the image does not change, but the angle of view becomes larger, which is a feeling, not a fact; D, the statement is wrong, the elderly read the book through a magnifying glass, and see the virtual image of the word, which is the use of a convex lens to magnify the upright virtual image Therefore, choose A

Answer B analysis: (1) Diffuse reflection occurs when light is applied to uneven objects;

2) The light of the object in the water will be refracted through the water surface, the refracted ray is far away from the normal, and the refracted ray will see the virtual image of the object shallower than the object in the water;

3) The rainbow in the sky after rain is a phenomenon formed by the refraction of sunlight by small water droplets in the air;

4) The dispersion phenomenon of light shows that white light is composed of seven kinds of monochromatic light Answer: a. Wrong, frosted glass is uneven, which can make the light diffuse reflection, so that you can see the words on the blackboard from different angles;

b. Correct, due to the refraction of light, we see that the depth of the water in the pool is shallower than it actually is;

c. False, the rainbow in the sky after the rain is formed due to the refraction of light;

d. Error, the dispersion phenomenon of light proves that white light is a polychromatic light, which is composed of seven monochromatic lights;

Therefore, choose B Comment: This question mainly examines the phenomenon of diffuse reflection, the refraction of light, and the dispersion of light, etc., which are all basic knowledge

Answer D analysis: In life, laser collimation, small hole imaging, shadow formation, solar and lunar eclipses, etc., all show that light propagates in a straight line in the same homogeneous medium;

When the light hits the interface between the two substances, a part of the light is reflected back to the original medium, which is the reflection of light, and the phenomena include: plane mirror imaging, inverted virtual shadow in water, etc.;

When light is obliquely emitted from one medium into another, the direction of propagation changes, which is the refraction of light, and the phenomena are: seeing the fish in the water shallower than the actual position, rainbows, lens imaging, etc

Answer: a. The rainbow in the sky after rain is formed by dispersion after sunlight is refracted by small water droplets in the air, and has nothing to do with the straight propagation of light; therefore a error;

b. When light enters water from air, the propagation direction does not necessarily change, and the vertical advance difference does not change the propagation direction, so B is wrong;

c. People can see through the calm surface of the lake that their faces are made on the surface of the water, which is formed by the reflection of light; Therefore c is wrong;

d. Under light irradiation, the shadow of the pole on the ground is formed by the straight line propagation of light, which can be explained by the straight line propagation law of light;

Therefore, choose d Comments: Generally speaking: seeing shadows, solar and lunar eclipses, and small hole imaging are related to the principle of linear propagation of light; Seeing mirrors, reflections, and periscopes is linked to the principle of reflection of light; When you see an object in water, you can see it through a glass or a lens to refract light

Answer D Analysis: Answer: Diffuse reflection also follows the law of reflection of light, the propagation speed of light in different media, the application of light propagation along a straight line, and the principle of plane mirror imaging

Answer: a. Both specular reflection and diffuse reflection obey the law of reflection of light, so A is wrong;

b. The propagation velocity of light in different media is different, so B is wrong;

c. The lunar eclipse is formed due to the straight propagation of light, so C is wrong;

d. The plane mirror can be imaged, and the virtual image is the same up and down, opposite to the left and right, and equal to the large upright; It is also possible to change the propagation path of light, so d is correct

Therefore, choose D Comments: This question involves several knowledge points of optics, which is more comprehensive, and two points should be paid attention to:

Diffuse reflection also obeys the law of reflection of light;

The plane mirror can change the propagation path of light, but it cannot change the nature of the beam