1. Everything that makes a sound is vibrating. When the vibration stops, so does the sound. Solids, liquids and gases all make sounds due to vibration.
2. Sound transmission needs medium (solid, liquid, gas).
Vacuum cannot transmit sound, but sound travels in the form of waves.
4. The speed of sound is related to the type and temperature of the medium. Generally speaking, sound is the fastest in solid, the fastest in liquid and the slowest in gas. The speed of sound in the air is 340 meters per second.
5. Listening process: sound wave-tympanic membrane vibration-auditory bone vibration-auditory nerve-brain bone preaching: sound wave-skull-jaw bone-auditory nerve-brain.
6. Binaural effect: the time and intensity of sound reaching both ears are different.
Through the binaural effect, we can distinguish the direction of sound and produce a three-dimensional sense.
7. Tone refers to the level of sound. (1) Frequency: 1 second The number of times of vibration reflects the speed of vibration. The faster an object vibrates, the greater its frequency. (2) Pitch is related to the vibration frequency of the vocal body: the higher the frequency, the higher the pitch, the lower the frequency and the lower the pitch. Human hearing is 20hz-20000Hz.
8. Loudness refers to the size of sound. (1) amplitude is the amplitude of the object vibration. (2) Loudness is related to the amplitude of the loudspeaker. The greater the amplitude, the greater the loudness, which is also related to the distance of the speaker. The farther the distance, the more dispersed the sound and the less loudness.
9. Timbre refers to the characteristics of sound. The timbre is related to the structure and material of the vocal body.
10. Tone, timbre and loudness are the three elements of sound. However, the loudness of treble is not necessarily high, and vice versa.
1 1. Four major pollutions: noise pollution, air pollution, water pollution and solid waste pollution. From the physical point of view, noise is the sound produced when the vocal body vibrates irregularly. From the perspective of environmental protection, any sound that interferes with people's normal rest, study and work, as well as the sound that interferes with people's listening.
1 1, decibel (dB): indicates the intensity of sound. 0 dB: People can only hear the faintest sound. 30-40 dB: Ideal quiet environment. In order to ensure rest and sleep, the sound should not exceed 50 dB, in order to ensure work and study, the sound should not exceed 70 dB, and in order to protect hearing, the sound should not exceed 90 dB.
12. Noise control: it is weakened at the sound source, weakened during propagation and weakened at the human ear.
13. Sound can transmit information, such as B-ultrasound, and can also transmit energy, such as cleaning clocks and removing stones. The method by which bats use echoes to determine their targets is called echolocation. According to the principle of echo location, sonar was invented.
14. Only when the time interval between the original sound and the echo is greater than 0. 1 sec (or the distance from the obstacle is 17m) can the echo be generated.
Echo distance measurement: 2s=vt
Chapter II Basic knowledge of light phenomenon
1. light source: an object that can emit light by itself. The sun is a natural light source, while electric lamps and candle flames are artificial light sources. The moon and all the stars are not light sources.
2. Light propagates in a straight line in the same uniform medium. It can explain the shadow formation and pinhole imaging.
3. The speed of light in vacuum is the fastest in the universe, represented by the letter C: c=3× 108 m/s The speed of light in water is about 3/4 of that in vacuum.
The speed of light in glass is two-thirds of that in vacuum.
When light meets the surface of water, glass and many other objects, it will be reflected. The reflection of light follows the law of reflection. (1) The reflected light, incident light and normal line are in the same plane (2) The reflection angles of the reflected light and incident light on both sides of the normal line (3) are equal to the incident angle.
5. In the reflection phenomenon, the light path is reversible. Reflection is divided into specular reflection and diffuse reflection. Specular reflection: the surface is smooth, parallel light is incident, and the reflected light is still parallel. Diffuse reflection: the surface is rough, parallel light is incident, and light is reflected in all directions.
6. When light obliquely enters another medium from one medium, the propagation direction is deflected, which is called light refraction. When refraction occurs, emission must also occur. The optical path in refraction is also reversible.
7. When light is obliquely incident from air into water or other media, the refracted light will be deflected to the normal direction. The law of refraction of light: three lines * * * plane, two lines are divided into two sides, and the two angles are not equal (the angle is larger in air). Refraction phenomenon: pen dislocation, shallow pool, fish in the water, mirage, etc.
8. The phenomenon that a beam of white light (sunlight) is decomposed into seven colors of red, orange, yellow, green, indigo and purple through a prism is called optical dispersion. It shows that white light is not monochromatic light, but synthetic light composed of various monochromatic lights. Rainbow is the scattering of sunlight by water droplets.
9. The three primary colors of light: red, green and blue pigments: the colors of cyan, yellow and magenta transparent objects are determined by their colored light, and the colors of opaque objects are determined by their reflected colored light.
10, infrared rays are located outside the red light, and all objects are constantly emitting infrared rays. The higher the temperature of an object, the more infrared rays it radiates, and the object is also absorbing infrared rays. Infrared action:
① Thermal action: heating food thermogram for diagnosis ② Infrared remote sensing: earth survey, water source search, forest fire monitoring, etc. ③ Remote control: TV, air conditioner, etc.
1 1. Ultraviolet rays are located outside the violet light, and sunlight is an important source of natural ultraviolet rays. Ozone can absorb ultraviolet rays and avoid the harm of excessive ultraviolet rays to human body. The function of ultraviolet ray: ① sterilization: ultraviolet lamp in hospital ② fluorescence function of ultraviolet ray: money detector and anti-counterfeiting; ③ Proper ultraviolet irradiation is beneficial to the synthesis of vitamin D, the absorption of calcium and the growth and health of human bones.
Chapter III Lenses and Their Applications
1. A lens with a thick middle and a thin edge is called a convex lens, and a lens with a thick edge and a thin middle is called a concave lens. Light passing through the optical center will not change its propagation direction.
2. A convex lens has two real focal points, and the distance from the focal point to the optical center is called the focal length. A concave lens has two virtual focal points.
3. Convex lens can condense light, while concave lens can diverge light.
4. Three kinds of special light: ① The light passing through the optical center does not change its propagation direction. ② The light parallel to the main optical axis passes through the focal point after refraction. For concave lens, its focus is virtual focus, which is the reverse extension line of refracted light. ③ The refracted light passing through the focal point is parallel to the main optical axis. For concave lens, it is virtual focus, which is the forward extension line of incident light passing through the focus.
5. The lens of the camera is a convex lens, and the function of the focusing ring is to adjust the distance between the lens and the film. When shooting close-up, the lens stretches forward.
When shooting a distant view, the lens retracts, the aperture controls the amount of light, and the shutter controls the exposure time.
6.
U & gt2f Inverted Miniature Reality Camera
U=2f handstand equals reality.
F<u & lt2f Inverted Amplification Real Projector
U=f is not like a picture.
U<f vertical magnifying virtual magnifying glass
Dual focal length is divided into virtual and real, dual focal length is divided into size, and real and virtual are used for imaging. The size and distance of the image are fixed, and the image runs with the object.
7. The eye is like a camera, the lens is equivalent to a convex lens, and the retina is equivalent to a light screen. The apparent distance is 25cm. Hyperopia can see distant objects clearly, but can't see near ones clearly. The lens is too thin and imaged behind the retina. Myopia can see the near objects clearly, but can't see the distant objects clearly. The lens is too thick and imaged in front of the retina.
8. There should be concave lenses for myopia and convex lenses for hyperopia. Glasses power = 100× power = 1/f
9. The eyepiece and objective lens of a telescope are convex lenses, the eyepiece is equivalent to a magnifying glass, and the objective lens is equivalent to a camera lens. The eyepiece and objective lens of a microscope are also convex lenses, the eyepiece is equivalent to a magnifying glass, and the objective lens is equivalent to a projection lens.
Chapter IV Changes in the Situation
1. Temperature is how hot or cold an object is.
2. Thermometer principle: It is made by using the property that liquid expands when heated and contracts when cooled. Precautions before use: ① Observe its range ② Identify its dividing value. Attention when using: ① Put all the glass bubbles of the thermometer into the liquid to be measured, and don't touch the bottom or wall of the container; ② Put the glass bulb of the thermometer into the liquid for a while; After stabilization, when reading ③, the thermometer should not leave the measured liquid (except the thermometer) and the line of sight should be flush with the thermometer liquid column.
The change of matter from one state to another is called the change of matter state. The change from solid to liquid is called melting, and the change from liquid to solid is called solidification. Melting absorbs heat and solidification releases heat. Solids are divided into crystalline and amorphous.
The change from liquid to gas is called vaporization, and the change from gas to liquid is called liquefaction. Vaporization absorbs heat and liquefaction releases heat. Vaporization is divided into evaporation and boiling. Evaporation: slow evaporation on the surface of a liquid at any temperature. Factors affecting evaporation: ① temperature of liquid; ② Surface area of liquid; (3) Boiling speed of air flow on liquid surface: at a certain temperature, the phenomenon of violent evaporation inside and on the surface of liquid.
5. There are two methods of liquefaction: lowering temperature and compressing volume.
6. The change of a substance from a solid state to a gaseous state is called sublimation, which absorbs heat, and the change from a gaseous state to a solid state is called sublimation to release heat.
Chapter V Current and Circuit
1. Making an object charged by friction is called triboelectrification, and charged objects can attract light and small objects. Nature has only positive and negative charges. The glass rod rubbed by silk is positively charged, while the rubber rod rubbed by fur is negatively charged. The same charges repel each other and different charges attract each other.
2. The amount of charge is called the amount of charge. Unit: Coulomb (C) Element charge is the smallest charge. E =1.6×10-19 atom consists of positively charged nuclei and negatively charged electrons. In general, the positive charge of the nucleus is equal to the negative charge of the total electrons outside the nucleus, and it does not show electricity, but it shows negative charge when it gains electrons and positive charge when it loses electrons.
3. The directional motion (positive or negative) of charge forms current. The directional movement direction of positive charge is defined as the current direction. Power supply is a device that provides electric energy, and electrical appliances are devices that consume electric energy. The switch controls the on-off of the circuit, and the wire connects the circuit.
4. Outside the power supply: the direction of current flows from the positive pole of the power supply to the appliance and then to the negative pole; Inside the power supply: the direction of current flowing from the negative pole to the positive pole of the power supply.
5. Access: The circuits and appliances connected everywhere are working normally. Open circuit: the circuit is broken, and the electrical appliance cannot work without current. Short circuit: connect the wires directly to both ends of the power supply without electrical appliances.
6. An object that is good at conducting electricity is called a conductor, and an object that is not good at conducting electricity is called an insulator. Metals conduct electricity by free electrons, and acid-base salt solutions conduct electricity by positive and negative ions.
7. The current represents the physical quantity of the current intensity, which is expressed by I ... a)1a =1000 ma1ma =1000 ua.
8. Pay attention to the use of ammeters (two are required, two are not required): ① ammeters should be connected in series in the circuit; ② Current flows into ammeters from "+"terminals; ③ The measured current should not exceed the range of ammeters; ④ Never connect ammeters directly to both ends of the power supply without using electrical appliances. Attention should also be paid to: ① Before using the ammeter, observe whether the pointer of the ammeter points to zero, and if not, set it to zero first; (2) Starting from the terminal with larger range, select the measuring range by touching.
The current in the series circuit is equal everywhere, and the current in the main circuit of the parallel circuit is equal to the current in each branch.