1. Physics is the study of sound, light, heat, electricity and force.

2. Sound is produced by the vibration of objects. The spread of sound needs media. Vacuum can't transmit sound.

3. Three characteristics of sound:

① Tone: It is determined by the vibration frequency of the object. The faster the frequency, the higher the pitch.

(2) Loudness: It is determined by the vibration amplitude of the object. The greater the amplitude, the greater the loudness.

(3) Tone: It is determined by the material and structure of the object, and the tone of different objects is different.

4. The basic process of people hearing sound:

① Tympanic membrane vibration → ossicles and other tissues → auditory nerve → brain.

② Jaw and skull → auditory nerve → brain.

5. The function of sound: transmitting information and energy (for example)

6. Any sound that affects people's normal study and life is noise. In order to protect hearing, the sound should not exceed 90dB；; In order to ensure work and study, the sound should not exceed 70dB；; In order to ensure rest and sleep, the sound should not exceed 50 decibels.

(2) the change of material state

1. temperature: the degree of heat and cold of an object is called temperature. Unit: Celsius (℃) Provisions: the temperature of ice-water mixture is-0℃; Boiling water temperature-100℃

2. Thermometer principle: It is made by using the characteristics of liquid expanding when heated and contracting when cooled. Commonly used liquids are mercury, alcohol, kerosene, etc. 3. Use of the thermometer: Take a look: Before use, you must first see the range and dividing value of the thermometer; Second discharge: the glass bubble is completely immersed in the liquid and cannot touch the bottom and wall of the container;

Third reading:

○ 1 Read again after the thermometer is stable;

2 reading glass bubbles can't leave the liquid level;

3 reading, eyes should be flush with the upper surface of the thermometer liquid column.

4. Thermometer: measuring range: 35℃ ~ 42℃; Division value: 0.1℃; Drop the mercury before using it.

5. The process of changing a substance from a solid state to a liquid state is called melting; Melting requires heat. The process of changing a substance from a liquid state to a solid state is called solidification; Curing is exothermic. The process of changing a substance from a liquid state to a gas state is called vaporization; Vaporization requires heat absorption. The process of changing a substance from a gaseous state to a liquid state is called liquefaction; Liquefaction is exothermic. The process of changing a substance from a solid to a gas is called sublimation; Sublimation requires heat absorption. The process of changing a substance from a gaseous state to a solid state is called sublimation; Condensation gives off heat.

6. Common crystals are ice, waves and various metals; Amorphous crystals include wax, asphalt, rosin, glass, etc. It is necessary to distinguish the melting and solidification images of crystals from the amorphous images.

7. The crystal should absorb heat during the melting process, but the temperature remains the same; In the process of solidification, heat should be released, but the temperature remains the same; The melting point and freezing point of the same crystal are the same. Amorphous crystals absorb heat during melting, and the temperature keeps rising. In the process of solidification, heat will be released and the temperature will drop continuously.

8. There are two ways of vaporization: boiling and evaporation.

1 boiling:

A. Definition: At a certain temperature, the surface and the interior of the liquid are violently vaporized at the same time.

B. Boiling conditions: ① reaching the boiling point; ② Continue heating.

C boiling characteristics: liquid absorbs heat when boiling, but the temperature remains unchanged.

2 evaporation:

One definition: at any temperature, gasification only occurs on the surface of liquid.

B. Factors affecting evaporation speed: the speed of air flow on the liquid surface: the faster the air flow, the faster the evaporation; Liquid temperature: the higher the temperature, the faster the evaporation; Size of liquid surface area: The larger the surface area, the faster the evaporation.

C. evaporation has a cooling effect.

8. There are two ways to liquefy: lowering the temperature and compressing the volume.

9. It can explain various physical changes in daily life. Such as: fog, dew, frost, hail, the formation of snow, all kinds of "white gas", ice flowers by the window, sanitary balls become smaller, the lamp tube turns black, the filament becomes thinner, ice turns into water, and molten iron turns into steel.

10. The boiling point of water is related to atmospheric pressure: the higher the atmospheric pressure, the higher the boiling point. The higher the altitude, the higher the air pressure and boiling point. )

(3) Light phenomenon

1. Propagation speed of light in vacuum: c = 3×108m/s.

2. The propagation speed of sound in the air: V = 340m m/s..

3. Meta-charge: e =1.6×10–19c. Key knowledge

1. Light travels in a straight line in the same uniform medium. (such as laser-guided tunnel, solar eclipse, lunar eclipse, shadow formation, "three points and one line" for aiming, pinhole imaging, etc. Are obtained by using the principle of linear propagation of light. )

2. Light source:

○ 1 Natural light sources: such as jellyfish, sun, fireflies, etc.

○2 Artificial light sources: such as electric lights, flashlights, candles, etc. (Note: No, the moon is the light source)

3. The three primary colors of light: red, green and blue.

Light will be reflected on the surface of any object.

5. Law of light reflection:

(1) Incident light, normal light and reflected light are in the same plane (three lines are in the same plane).

(2) The incident light and the reflected light are separated on both sides of the normal.

③ reflection angle i= incident angle r

Law of refraction of light:

① When light enters other media from air, refracted light is deflected to the normal direction.

② When light enters the air from other media, the refracted light is far away from the normal. Imaging characteristics of plane mirror;

(1) The image and the object are equal in size.

② The distance from the image to the plane mirror is equal to the distance from the object to the plane mirror (equidistant).

③ The connecting line between the image and the object is perpendicular to the plane mirror. (vertical)

(4) Plane mirror image is a virtual image. (Virtual image)

6. In the reflection and refraction of light, the light path is reversible.

7. There are two kinds of reflection: specular reflection and diffuse reflection (for example).

8. The role of infrared rays The role of ultraviolet rays.

① Infrared remote control

① bactericidal action

② Infrared night vision device

(2) Let the fluorescent substance glow, and judge whether the substance is true or false.

(3) Detecting the health status of patients.

③ Promote the synthesis of vitamin D and help the absorption of calcium.

9. Spectral sunlight is decomposed into red, orange, yellow, green, blue, indigo and purple.

(4) Lens and its application

1. Convex lens: thick in the middle and thin in the edge.

2. Concave lens: thin in the middle and thick in the edge.

3. Convex lens has convergent effect on light, while concave lens has divergent effect on light.

4. Can find out the main optical axis, focal point and focal length.

5. Object distance (u)→ distance from object to convex lens. Image distance (v)→ the distance from the image to the convex lens. The law of convex lens imaging: the relationship between object distance and focal length, the relationship between image distance and focal length, imaginary and real u >；; 2f f<v & lt2f inverted reduction real image u=2f v=2f inverted equal real image f < u & lt2f v> inverted amplification of real image 2f u=2f does not form an infinitely magnified virtual image of image U < F Conclusion: One focus is divided into virtual reality and the other focus is divided into size. The close-up image of the object becomes larger and the close-up image of the object becomes smaller. The real image is upside down and the virtual image is upright.

6. camera: u > F becomes an inverted and reduced real image. Slide projector: f

7. Know the causes of myopia and hyperopia. Correction: myopia is corrected with convex lens (convex lens is negative); Hyperopia is corrected with concave lens (concave lens is positive).

8. Lens magnification: φ = 1/f (f → focal length