1. Physics is the study of physical phenomena such as sound, light, heat, electricity, and force.
2. Sound is produced by the vibration of an object. A medium is needed for sound to travel. A vacuum cannot transmit sound.
3. The three main characteristics of sound:
①Pitch: it is determined by the frequency of the vibration of the object, the faster the frequency, the higher the pitch.
② loudness: the amplitude of the vibration of the object is determined by the amplitude, the greater the amplitude, the greater the loudness.
③Tone: determined by the material and structure of the object, different objects have different tones.
4. people hear the basic process of sound:
① vibration of the tympanic membrane → auditory bones and other tissues → auditory nerve → brain
② jawbone, skull → auditory nerve → brain
5. the role of the sound: the transfer of information and transfer of energy (able to cite examples)
6. all the impact of the sound of the people's normal learning and living are is noise. In order to protect hearing, the sound should not exceed 90 dB; in order to ensure that work and study, the sound should not exceed 70 dB; in order to ensure that rest and sleep, the sound should not exceed 50 dB.
(2) Changes in Physical State
1. Temperature: the degree of heat or cold of an object is called temperature. Unit: degrees Celsius (℃) Provisions: the temperature of ice-water mixture -- 0 ℃; boiling water temperature -- 100 ℃
2. Thermometer principle: the use of liquid thermal expansion and contraction of the nature of the made. Commonly used liquids are mercury, alcohol, kerosene and so on. 3. The use of thermometers: a look: before using the thermometer to see the range and divisional value; two put: the glass bubble is fully submerged in the liquid, can not touch the bottom of the container and the container wall;
Three readings:
○ 1 to be stable thermometer signals and then readings;
○ 2 readings of the glass bubble can not leave the surface of the liquid;
○ 3 readings of the eyes to be level with the upper surface of the liquid column of the thermometer. The eye should be level with the upper surface of the thermometer when reading.
4. thermometer: range: 35 ℃ ~ 42 ℃; graduated value: 0.1 ℃; before using the mercury to shake down.
5. change of state of matter from solid to liquid process called melting; melting to absorb heat. Substance from liquid to solid process called solidification; solidification to exothermic. Substances from the liquid state into a gaseous process called vaporization; vaporization to absorb heat. The process of changing a substance from a gas to a liquid is called liquefaction; liquefaction is exothermic. The process of changing a substance from a solid to a gas is called sublimation; sublimation absorbs heat. The process of changing a substance from a gas to a solid is called condensation; condensation is exothermic.
6. Common crystals are ice, sea waves, various metals; amorphous wax, asphalt, rosin, glass and so on. Required to be able to distinguish between crystals and amorphous melting and solidification images.
7. crystals in the melting process to absorb heat, but the temperature remains the same; in the solidification process to exothermic, but the temperature remains the same; the same crystal melting point and solidification point is the same. Non-crystalline in the melting process to absorb heat, the temperature continues to rise; in the solidification process to exothermic, the temperature continues to fall.
8. There are two types of vaporization: boiling and evaporation.
○1 boiling:
a. Definition: at a certain temperature, at the surface of the liquid and the internal phenomenon of intense vaporization occurs at the same time.
b. Boiling conditions: ① reach the boiling point; ② continue to heat.
c. Characteristics of boiling: the liquid in boiling to absorb heat, but the temperature remains unchanged
○2 evaporation:
a. Definition: at any temperature, only the surface of the liquid vaporization phenomenon.
b. Factors affecting the speed of evaporation: the speed of air flow on the surface of the liquid: the faster the air flow, the faster the evaporation; liquid temperature: the higher the temperature, the faster the evaporation; the size of the surface area of the liquid: the larger the surface area, the faster the evaporation.
c. Evaporation has a cooling effect.
8. liquefaction has two ways: reduce the temperature and compress the volume
9. can explain a variety of physical changes in daily life. Such as: fog, dew, frost, hail, the formation of snow, a variety of "white gas", the window of the ice, sanitary ball smaller, black lamps, filament thinning, ice into water, iron into steel parts.
10. The boiling point of water is related to atmospheric pressure: the higher the pressure, the higher the boiling point. (The higher the altitude, the higher the air pressure, the higher the boiling point.)
(3) Phenomenon of light
1. Speed of propagation of light in vacuum: c = 3 × 10 8 m/s
2. Speed of propagation of sound in air: v = 340 m/s
3. Meta-charge: e = 1.6 × 10 -19 C II. Essential Knowledge
1. Light travels in a straight line in a homogeneous medium. (eg: laser-guided tunneling, the formation of solar and lunar eclipses, the formation of shadows, aiming with the "three dots and one line", small hole imaging, etc. are obtained by using the principle of linear propagation of light.)
2. light sources:
○1 natural light sources: such as jellyfish, the sun, fireflies and so on.
○2 Artificial light sources: such as electric lamps, flashlights, candles and so on. (Note: not the moon is a light source)
3. The three primary colors of light: red, green, and blue.
4. Light reflects off the surface of any object.
5. The law of reflection of light:
1) the incident ray, the normal ray, the reflected ray in the same plane (the three lines of the same plane)
2) the incident ray, the reflected ray on both sides of the normal.
③ angle of reflection i = angle of incidence r
Law of refraction of light:
① light from the air into other media, the refracted rays of light to the normal deflection.
② light from other media into the air, refracted light away from the normal. Plane mirror imaging characteristics:
① image and object of equal size (equal size)
② image to the plane mirror distance is equal to the distance from the object to the plane mirror (equidistant)
③ image and the object of the line perpendicular to the plane mirror. (Perpendicular)
④ The plane mirror forms an imaginary image. (Imaginary image)
6. In both the phenomenon of reflection and refraction of light, the path of light is reversible.
7. There are two kinds of reflection: specular and diffuse reflection (can give examples)
8. The role of infrared The role of ultraviolet.
① infrared rocker
① sterilization
② infrared night vision
② make fluorescent substances glow to determine the authenticity of the substance
③ detection of the patient's health
③ to promote the synthesis of vitamin D, to help the absorption of calcium
9. Spectrum of the sun's light decomposition into: red, orange, yellow, green, Blue, indigo, violet.
(4) Lenses and their applications
1. Convex lens: thick in the center and thin at the edges.
2. Concave lens: thin in the center, thick at the edges.
3. Convex lenses converge light and concave lenses diverge light.
4. Be able to find the principal optical axis, focus, and focal length.
5. Object distance (u) → distance from object to convex lens. Image distance (v) → distance from the image to the convex lens. Convex lens imaging laws: object distance and focal length relationship image distance and focal length relationship image positive, inverted image of large, small image of virtual, real u>2f f<v<2f inverted shrunken solid u=2f v=2f inverted equal solid f<u<2f v>2f inverted enlarged solid u=2f not image u<f infinite distance orthogonal enlarged virtual image Conclusion: a focal length, two focal lengths, size. Conclusion: One focal length separates the real from the imaginary, and the second focal length separates the size. The image becomes larger when the object is nearer and smaller when the object is farther away and nearer. All real images are inverted and all virtual images are upright.
6. Camera: u > f into an inverted, reduced real image. Slide projector: f < u < 2f forms an inverted, magnified solid image. Magnifying glass: u < f forms an upright, magnified virtual image. Microscope: eyepiece: to magnify; objective: f < u < 2f to form an inverted, magnified solid image Telescope: eyepiece: to magnify; objective: u > 2f , to form an inverted, magnified solid image.
7. Know the causes of myopia and hyperopia. Correction: myopia is corrected with a concave lens (concave lens is negative); hyperopia is corrected with a convex lens (convex lens is positive).
8. Lens focal length: Φ = 1 / f (f → focal length
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