The optics section of junior high school physics can help me review Ha 5

Be specific! You're asking too much of a question.

If the sun shines from the right, the moon cannot be on the right side of the earth, so it will be the sun's light, and the moon will not be visible if it is a new moon. c and d are at an angle of 90 between the sun and the moon and the earth, so the corresponding moon phase is the quarter moon (half), so c and d are excluded. So choose a and ask for adoption.

Memorize more, memorize more. Junior high school physics is very simple, there are very few things that need to be understood, memorize some things, and that's it.

Usually, you should think more about various optical path diagrams, and then pay attention to remember more typical cases, which is helpful.

When you do the problem, you draw the picture first, and then talk about other things.

Practice diligently.

Do more questions, and draw more pictures in the process.

Draw more pictures, experiment more, do more questions, classify more, and summarize more.

[The myopia lens is a concave lens, which has a divergent effect on light, and the light emitted by the candle in the second question can just converge and image on the light screen, but after being diverged by the concave lens in the third question, the angle between the light and the normal becomes larger, which is equivalent to the light source (candle) moving forward, so if you want to image, you have to move the candle back.] ]

If you don't understand, please continue to ask, and I'll be glad to answer.

If it works.

The myopia lens is a concave lens, which has a divergent effect on light, which means that if the myopia lens is not used, the image will be presented in front of the light screen, which will keep the candle away from the convex lens, which is equivalent to making the light screen close to the convex lens.

Myopic eyes can see clearly near and far because the lens has too strong refractive ability. When looking at something in the distance, the curvature of the lens cannot become small enough, as in question 3; But when the image is close to the eye, notice that the lens curvature becomes large enough to refract the image on the retina. The convex lens on the diagram cannot.

This is the reason why convex lenses cannot be considered as lenses at this time.

Straight line propagation of light: Light travels in a straight line in the same homogeneous medium. Aperture imaging, shadow, and spot are the phenomenon of linear propagation of light.

The maximum velocity of light in a vacuum is 3 10 8 m s 3 10 5 km s.

The law of reflection of light: one side, two sides, three equal sizes. [The angle between the incident ray and the normal is the angle of incidence.] The angle between the reflected ray and the normal is the reflection angle. 】

Imaging characteristics of plane mirror: virtual image, equal size, equal distance, symmetrical with the mirror surface. The reflection of an object in water is a reflection of light from a virtual image.

Refraction phenomena and laws of light: Seeing chopsticks and fish in the water is a phenomenon of light refraction.

Convex lenses have a converging effect on light, and concave lenses have a divergent effect on light. The law of refraction of light: one side, two sides, three with the big and four empty.

Convex lens imaging rule: [U=F does not image when U=2F V=2F becomes an inverted real image]

Object distance u image distance v properties of the image optical path diagram application.

u>2f f

Let's go through the basic concepts first and figure out the specific light.

The color of light The propagation of light.

1 Light source: An object that can be used by itself is called a light source.

2. Dispersion of light: The phenomenon of decomposing light into seven colors of light: red, yellow, green, blue, and violet, is called the dispersion of light.

3 The three primary colors of light: , the three primary colors of pigments: ,

4 Main features of infrared: thermal effect, application: heating, remote control, detection, night vision, etc.

5 The main characteristics of ultraviolet rays: make fluorescent substances glow, application: sterilization, money detection, etc., an appropriate amount of ultraviolet radiation is conducive to physical health, excessive exposure to ultraviolet rays is harmful to physical health, to protect.

6 Propagation of light in a straight line: Light travels along in . Aperture imaging, shadows, objects behind invisible objects, solar eclipses, lunar eclipses, belong to light in the same substance.

The maximum propagation velocity of light in a vacuum is m s, while the propagation velocity in air is also considered to be 3 108m s.

6 We can see objects that do not emit light because the light from these objects enters our eyes.

7 The law of reflection of light: the reflected rays and the incident rays, the normals are on , the reflected rays and the incident rays are separated from the normals, and the angle is equal to the angle. (Note: The optical path is reversible).

Diffuse reflection follows the same light as specular reflection.

10 Plane Mirror Imaging Features:

1) Image and object size (2) Distance from image to mirror The distance from the object to the mirror. (3) The connection between the image and the object and the mirror.

4) A flat mirror is a vertical image. Plane mirror applications: (1) imaging (2) changing the optical path.

Refraction of light. 1 Refraction of light: A phenomenon in which light generally changes when it is obliquely emitted from one medium into another.

2. The law of refraction of light: light enters water or other medium from air, and the refracted light and incident rays and normals are in; Refracted rays and incident rays are separated from normals, and the angle of refraction is the angle of incidence; When the angle of incidence increases, the angle of refraction also increases with ; The direction of propagation of light rays when they are directed perpendicular to the surface of the medium. (The refracted optical path is also

3 Convex lens: the lens at the middle edge, which has an effect on light, so it is also called a lens. Concave lenses have an effect on light.

4 Convex Lens Imaging:

Object distance (u) image distance (v) upright (inverted) magnification (reduction) real image (virtual image).

u>2f

U=2Ffu=F cannot be imaged.

uOptical path diagram of

1.Straight line propagation of light.

2.Reflection of light (emphasis).

3.Refraction of light (emphasis).

4.Dispersion of light.

5.Lens. 6.Convex lens imaging (focused).

7.Eyes, glasses.

I have a summary of the formula for junior high school.

Optics in junior high school is too simple.

With your own imagination and a rational mind, you will not be a problem in high school physics.