The Encyclopedia of Physics Knowledge of Minhang Senior High School Entrance Examination Chapter I Induction of Sound Phenomenon Knowledge
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 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.
882. The maximum propagation speed of light in vacuum is 3× 10 m/s, while the propagation speed in air is also considered to be 3× 10 m/s. ..
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.
Chapter 3: Knowledge induction 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), and becomes an inverted reduced real image (image distance: f2f). Such as a slide projector.
(3) The object is in the focal length (u0
Q amplifier = mq
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quart
Ohm's law:
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you are
Electric power formula: W = U I t
W = U I t combination W = U I t combination I If all electric energy is converted into internal energy, then: Q=W, such as an electric heater. Electric power formula:
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P = W /t P = I U
Current: In a series circuit, the current is equal everywhere. Expression: I=I 1=I2.
Voltage: The total voltage on the circuit is equal to the sum of the voltages of all parts of the circuit. Expression: U=U
1+
U2 partial pressure principle: U 1U2
R 1
In the R2 series circuit, the electrical power of the electrical appliance is proportional to the resistance. Expression:
Characteristics of parallel circuit:
P2R
Current: In parallel circuit, the current in the main circuit is equal to the sum of the currents in each branch. Expression: I=I 1+I22.
Infrared Radiation (infrared radiation)
Shunt principle: 1? 2
I2R 1
Hope to adopt