1. Sound generation: produced by the vibration of an object. When the vibration stops, so does the sound.

2. Sound transmission: Sound is transmitted through the media. Vacuum can't transmit sound. Usually the sound we hear comes from the air.

3. Sound speed: the speed of propagation in air is 340m/s ... Sound travels faster in solid than in liquid, and faster in liquid than in air.

4. Measure the distance by echo: S= 1/2vt.

5. Three characteristics of musical sound: tone, loudness and timbre. (1) Tone: refers to the sound level, which is related to the speaker's frequency. (2) Loudness: refers to the size of the sound, which is related to the amplitude of the speaker and the distance between the sound source and the listener.

6. Method of reducing noise: (1) at the sound source; (2) weakened in the process of transmission; (3) Weakening in human ears.

7. Audible sound: sound waves with a frequency between 20 Hz and 20000Hz: ultrasonic waves: sound waves with a frequency higher than 20000Hz; Infrasound: Sound wave with frequency lower than 20Hz.

8. Ultrasonic features: good directivity, strong penetration and concentrated acoustic energy. Specific applications are: sonar, B-ultrasound, ultrasonic velocimeter, ultrasonic cleaning machine, ultrasonic welding machine, etc.

9. Characteristics of infrasound: It can travel far, easily bypass obstacles and penetrate everywhere. Infrasound with a certain intensity will do harm to human body and even destroy mechanical buildings. It is mainly produced by natural volcanic eruption, tsunami earthquake and so on. In addition, human-made rocket launches, airplane flights, Mercedes-Benz trains and cars, nuclear explosions and so on. It can also produce infrasound waves.

Chapter II Knowledge Induction of State Change

1. temperature: refers to the degree of heat and cold of an object. The measuring tool is a thermometer, which is made according to the principle that liquid expands with heat and contracts with cold.

2. Celsius temperature (℃): The unit is Celsius. The regulation of 1℃: the temperature of ice-water mixture is 0℃, and the boiling water temperature at a standard atmospheric pressure is 100℃. Between 0℃ and 100, it is divided into 100 equal parts, and each equal part is 1℃.

3. The common thermometers are (1) laboratory thermometers; (2) thermometer; (3) thermometer.

Thermometer: The measuring range is 35℃ to 42℃, and each battery is 0.65438 0℃.

4. Use of thermometer: (1) Observe its measuring range and minimum calibration value before use; (2) When in use, the glass bulb of the thermometer should be completely immersed in the measured liquid to avoid touching the bottom or wall of the container; (3) the thermometer is stable before reading; (4) When reading, the glass bubble should stay in the liquid to be measured, and the line of sight should be flush with the upper surface of the liquid column in the thermometer.

5. Solid, liquid and gas are the three states of matter.

6. Melting: The process of changing a substance from solid to liquid is called melting. Absorb heat.

7. Solidification: The process of changing a substance from a liquid state to a solid state is called solidification. Give off heat.

8. Melting point and freezing point: the temperature at which the crystal remains unchanged when it melts is called melting point; . The temperature at which a crystal remains constant during solidification is called freezing point. The melting point and freezing point of crystals are the same.

9. Important difference between crystal and amorphous: crystal has a certain melting temperature (melting point), while amorphous has no melting point.

10. melting and solidification curves:

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1 1. (crystal melting and solidification curve) (amorphous melting curve)

12. In the above figure, AD is the crystal melting curve. The crystal is solid in AB section and melting in BC section, which absorbs heat, but the temperature is constant, and it is in solid-liquid state, while the CD section is in liquid state. DG is the crystal solidification curve, DE section is liquid, EF section is solidification process, exothermic and constant temperature, solid-liquid exists, and FG is solid.

13. vaporization: the process of changing a substance from a liquid state to a gas state is called vaporization, and the vaporization methods include evaporation and boiling. Both absorb heat.

14. Evaporation: it is a slow evaporation phenomenon only on the surface of liquid at any temperature.

15. Boiling: it is a violent vaporization phenomenon that occurs both inside and outside the liquid at a certain temperature (boiling point). When a liquid boils, it absorbs heat, but the temperature remains the same. This temperature is called boiling point.

16. Factors affecting the evaporation rate of liquid: (1) liquid temperature; (2) liquid surface area; (3) The velocity of air flow above the liquid surface.

17. Liquefaction: The process of changing a substance from a gaseous state to a liquid state is called liquefaction, which releases heat. The methods of liquefying gas are: lowering the temperature and compressing the volume. Liquefaction phenomena such as "white gas" and fog. )

18. Sublimation and Sublimation: The direct change of a substance from a solid state to a gas state is called sublimation, which requires heat absorption; The direct transformation of a substance from a gaseous state to a solid state is called sublimation, which requires heat release.

19. water cycle: the water in nature is constantly moving and changing, forming a huge water cycle system. The circulation of water is accompanied by energy transfer.

Chapter III Knowledge Induction of Light Phenomenon

1. light source: an object that can emit light by itself is called a light source.

Sunlight consists of red, orange, yellow, green, blue, indigo and purple.

3. The three primary colors of light are red, green and blue; The three primary colors of pigment are red, yellow and blue.

4. Invisible light includes infrared light and ultraviolet light. Features: infrared rays can make the irradiated object heat, which has thermal effect (such as the heat of the sun is transmitted to the earth through infrared rays); The most remarkable feature of ultraviolet light is that it can make fluorescent substances glow and sterilize.

1. Linear propagation of light: Light propagates in a straight line in a uniform medium.

2. The maximum propagation speed of light in vacuum is 3×108m/s, but it is also considered as 3×108m/s in air. ..

We can see objects that don't emit light because the light reflected by these objects enters our eyes.

4. The reflection law of light: reflected light is on the same plane as incident light and normal line, and the reflected light and incident light are separated on both sides of normal line, and the reflection angle is equal to the incident angle. (Note: the optical path is reversible)

5. Diffuse reflection and specular reflection follow the law of light reflection.

6. Imaging characteristics of flat mirror: (1) Flat mirror is a virtual image; (2) The image is the same size as the object; (3) The distance between the image and the object and the mirror is equal; (4) The connecting line between the image and the object is perpendicular to the mirror. In addition, the images and objects in the plane mirror are upside down.

7. Flat mirror application: (1) imaging; (2) change the light path.

8. Improper use of flat mirrors in life will cause light pollution.

Spherical mirrors include convex mirrors (convex mirrors) and concave mirror (concave mirror), both of which can image. Specific applications are: the rearview mirror of vehicles and the reflector of shopping malls are convex mirrors; The reflector of flashlight, solar cooker and the reflector worn on eyes are all concave mirror.

The fourth chapter summarizes the knowledge of light refraction.

Refraction of light: the phenomenon that the propagation direction of light generally changes when it obliquely enters another medium.

Law of refraction of light: light obliquely enters water or other media from the air, and the refracted light and the incident light are in the same plane and normal; Refracted light and incident light are separated on both sides of the normal, and the refraction angle is smaller than the incident angle; When the incident angle increases, the refraction angle also increases; When the light is perpendicular to the surface of the medium, the propagation direction remains unchanged. (Refractive light path is also reversible)

Convex lens: a lens with a thick center and a thin edge, which converges light, so it is also called a converging lens.

Convex lens imaging;

(1) The object exceeds the double focal length (U >；; 2f), converted into an inverted and reduced real image (image distance: f

(2) The object is between the focal length and the bifocal length (f; 2f). For example, a slide projector.

(3) the object in the focal length (u

Optical path diagram:

6. Matters needing attention in making light path diagram:

(1). Draw with tools; (2) It is the actual light that draws the solid line, but it is not the actual light that draws the dotted line; (3) The light should be shown by the arrow, and the light should be well connected without disconnection; (4) When making a reflection or refraction light path diagram, a line (dotted line) should be drawn at the incident point first, and then light should be made according to the relationship between reflection angle and incident angle or refraction angle and incident angle; (5) When light is refracted, the angle in the air is large; (6) The backward extension line of the light rays parallel to the main optical axis after diverging through the concave lens must intersect with the virtual focus; (7) When the plane mirror images, the reverse extension line of the reflected light must pass through the back image of the mirror; (8) When drawing a lens, be sure to draw a diagonal line on the lens as a shadow to represent the three-dimensional.

7. The human eye is like a magic camera, the lens is equivalent to the lens (convex lens) of the camera, and the retina is equivalent to the film in the camera.

8. Myopia can't see the distant scenery clearly, so you need to wear a concave lens; Long-sighted eyes can't see the nearby scenery clearly, so they need to wear convex lenses.

9. Telescopes can image distant objects at close range, in which the galileo telescope eyepiece is a concave lens and the objective lens is a convex lens; The eyepiece lenses of Kepler telescope are all convex lenses (the focal length of the objective lens is long and the focal length of the eyepiece is short).

10. The eyepiece objective of the microscope is also a convex lens (the focal length of the objective lens is short and the focal length of the eyepiece is long).