The first chapter "sound phenomenon" review overview.

First, the occurrence and spread of sound.

1 phenomenon, textbook P 13, figure 1. 1- 1 shows that all objects that make sounds are vibrating. When you hold down the tuning fork, the pronunciation stops, which means the vibration stops and the sound stops. Sound source of vibrating object.

Exercise: ① People speak and sing by the vibration of vocal cords, tactfully singing by the vibration of singing membrane, and crisp crickets by the friction of their wings. The vibration frequency must be between 20 and 20,000 times per second.

② In the lyrics of the Yellow River Chorus, "The wind is roaring, the horse is barking, and the Yellow River is roaring". The sound sources of "growl", "dog bark" and "growl" here are air, horse and Yellow River water respectively.

(3) Knock on the table and hear the sound, but you can't see the vibration of the table. What can you think of to prove the vibration of the table? You can sprinkle some pieces of paper on the table and it will jump when you knock on the table.

2. Sound needs medium to spread, and vacuum cannot spread sound. Sound travels in the air as invisible sound waves. When the sound waves reach people's ears, the eardrum vibrates, and people hear the sound.

Exercise: ① ① The experiment shown in P14 1. 1-4 can draw a conclusion that sound can't propagate in vacuum, and there is no air on the moon, so the astronauts who landed on the moon should talk by wireless phone even if they are very close, because radio waves can also propagate in vacuum, and the propagation speed of radio waves is 3×1.

(2) "Wind, rain, reading and the sound in the ear" means that gas, liquid and solid can make sounds, and air can spread sounds.

3. The speed of sound propagation in the medium is simply called the speed of sound. Generally speaking, the sound of V is solid >: V liquid > V gas travels at a speed of 340m/s or 1224km/h in air at 15℃ and at a speed of 0m/s in vacuum. ..

Exercise: ☆ There is a steel pipe filled with water, the length of which is L. Knock at one end and listen three times at the other. The propagation time from short to long is

4. Echo is formed because the sound meets obstacles and is reflected back in the process of propagation. If the echo reaches the human ear more than 0. 1s later than the original sound, the human ear can distinguish the echo from the original sound. At this time, the distance from the obstacle to the listener is at least 17m. Talking indoors sounds louder than in the wilderness, because the space in the room is relatively small, resulting in the echo reaching the human ear less than 0. 1s later than the original sound. Finally, the echo and the original sound are mixed together to strengthen the original sound.

Utilization: Echo can be used to measure the depth of the seabed, the distance of icebergs and the distance of enemy submarines. In the measurement, we must first know the speed of sound propagation in seawater. The measurement method is: measure the time t from the sound emission to the reflection of the sound signal, and find out the propagation speed v of the sound in the medium, then the distance between the sound point and the object S=vt/2.

Third, the sound of music and its three characteristics

1. Music is the sound made when an object vibrates regularly.

2. Tone: The level of sound that people feel. When you draw a piece of hard paper on the teeth of a comb, you can find a fast pitch. When you pull rubber bands with different thicknesses with the same force, you can find that the rubber bands vibrate and make a fast sound.

Turn it up. Combining the two experimental phenomena, you get the same conclusion: the tone is related to the vibration frequency of the speaker, and the higher the frequency, the higher the tone; The lower the frequency, the lower the pitch. The number of times an object vibrates at 1s is called frequency. The faster the object vibrates, the higher the frequency. Frequency per second is also recorded as Hz.

Exercise: Explain that bees can be found by hearing, but why can't butterflies hear them? The vibration frequency of bee wings is within the hearing range of human ears, while that of butterflies is not.

3. Loudness: the volume of sound felt by the human ear. Loudness is related to the amplitude of the generator and the distance from the sound. When an object vibrates, the maximum distance from its original position is called amplitude. The greater the amplitude, the greater the loudness. The main way to increase loudness is to reduce the divergence of sound.

Exercise: ☆ The bass singer sings loudly and the soprano sings softly for him: the soprano is loud and low, and the bass is low.

Fourth, the harm and control of noise

1. Four major pollutions in contemporary society: noise pollution, water pollution, air pollution and solid waste pollution.

2. From the physical point of view, noise refers to the sound produced when the vocal body vibrates irregularly and disorderly; Environmental protection angle noise refers to the sound that interferes with people's normal rest, study and work and the sound that people want to hear.

3. People use decibels (dB) to divide the sound level; The lower limit of hearing is 0 dB; In order to protect hearing, the noise should be controlled within 90dB；; In order to ensure work and study, the noise should be controlled within 70dB；; In order to ensure rest and sleep, the noise should be controlled within 50dB.

4. Ways to reduce noise: at the sound source, in the process of propagation, at the human ear.

Chapter II Overview of Light Phenomenon

First, the straight-line propagation of light

1, light source: Definition: An object that can emit light is called a light source.

Classification: natural light sources, such as the sun and fireflies; Artificial light sources, such as bonfires, candles, oil lamps and electric lights. The moon itself does not shine, it is not a light source.

2. Law: Light travels in a straight line in the same uniform medium.

3. Light is an ideal physical model abstracted from a small beam of light, and establishing an ideal physical model is one of the common methods to study physics.

5, the speed of light:

The speed of light in vacuum c = 3×108m/s = 3×105km/s; The speed of light is about 3× 108 m/s in air, 3/4 in water and 2/3 in glass.

Second, the reflection of light.

1. Definition: When light is emitted from one medium to the surface of another medium, part of the light is reflected back to the original medium, which is called light reflection.

2. Law of reflection: Three lines are in the same plane, the normal is in the middle, the two angles are equal, and the optical path is reversible. That is, the reflected light is on the same plane as the incident light and the normal line, and the reflected light and the incident light are separated on both sides of the normal line, and the reflection angle is equal to the incident angle. The light path is reversible in the process of light reflection.

3. Classification:

(1) specular reflection:

Definition: parallel light incident on the surface of an object is still parallel after reflection.

Condition: The reflecting surface is smooth.

Application: looking at the calm water facing the sun, it is particularly bright. The blackboard "reflects light" and so on, all because of specular reflection.

(2) Diffuse reflection:

Definition: parallel light incident on the surface of an object reflects in different directions, and each light obeys the law of light reflection.

Condition: The reflecting surface is uneven.

Application: You can see non-luminous objects from all directions, because light will diffuse when it hits an object.

4. Mirror:

(1) plane mirror:

Imaging characteristics: equal, equidistant, vertical, virtual image

(1) like, equal size.

② The distance between the image and the object and the mirror is equal.

③ The line between the image and the object is perpendicular to the mirror.

The image of an object in a plane mirror is a virtual image.

Imaging principle: reflection theorem of light

Purpose: imaging, changing light path.

Real image and virtual image: real image: the image formed by the convergence point of actual light.

Virtual image: an image formed by the convergence point of the reverse extension line of reflected light.

(2) spherical mirror:

Definition: Use the inner surface of the sphere as the reflecting surface.

Properties: concave mirror can converge the parallel light rays directed at it at one point; The reflected light from the focal point to concave mirror is parallel light.

Applications: solar cookers, flashlights, car headlights.

Definition: Use the outer surface of the sphere as the reflecting surface.

Properties: Convex mirror diverges light. The image formed by convex mirror is a reduced virtual image.

Third, color and invisible light.

The composition of white light: red, orange, yellow, green, blue, indigo and purple.

The three primary colors of colored light are red, green and blue. The three primary colors of pigment are magenta, yellow and cyan.

2. Invisible light: infrared ray and ultraviolet ray.

Chapter III Overview of Lenses and Their Applications

First, the refraction of light

1. Definition: When light obliquely enters another medium from one medium, the propagation direction generally changes; This phenomenon is called refraction of light.

2. The refraction law of light: three lines are in the same plane, the normal is in the middle, the angle in air is large, and the optical path is reversible.

(1) refracts light, and the incident light is in the same plane as the normal.

⑵ Refracted light and incident light are separated from normal.

(3) When light obliquely enters water or other media from the air, the refraction angle is smaller than the incident angle, which belongs to near normal refraction.

When light enters the air obliquely from water or other media, the refraction angle is greater than the incident angle, which belongs to far normal refraction.

Light is vertically incident from air (or emitted from other media), and the angle of refraction = incident angle = 0 degrees.

3. Application: Look at the objects in the water from the air, or look at the objects in the air from the water and see the virtual image of the objects. The position you see is higher than the actual position.

Exercise: ☆ The reason why the water in the pool looks shallower than the actual water is because the light is refracted when it is projected obliquely into the air from the water, and the refraction angle is greater than the incident angle.

☆ Blue sky and white clouds form reflections in the lake, and fish in the water walk freely in the "clouds". The white clouds in the water we see here are virtual images formed by the reflection of light, and the fish we see are virtual images formed by the refraction of light.

Second, the lens

1, noun: thin lens: the thickness of the lens is much smaller than the radius of the sphere.

Principal optical axis: a straight line passing through the centers of two spherical surfaces.

Optical center: (o) the center of the thin lens. Property: the direction of light propagation through the optical center is unchanged.

Focus (f): The point on the main optical axis where the convex lens can converge the light parallel to the main optical axis is called focus.

Focal length (f): the distance from the focal point to the optical center of the convex lens.

2. Typical optical path

It has a divergent effect on light.

3. Fill in the form:

3. The imaging law of convex lens and its application

1. Experiment: During the experiment, the candle is lit, so that the centers of the candle flame, convex lens and light screen are approximately at the same height. The purpose is to make the image of the candle flame in the center of the light curtain.

No matter how you move the screen in the experiment, you can't get an image on the screen. The possible reasons are as follows: ① candles are in focus; ② The candle flame is in the focus ③ The centers of the candle flame, convex lens and light shield are not at the same height; ④ The distance from the candle to the convex lens is slightly larger than the focal length, and the image is far away, so it is impossible to move the light screen of optical bench to this position.

2. Experimental conclusion: (convex lens imaging law)

F is empty and real, 2f is big, real and empty and positive,

See the table below for details:

The nature of object image range and its application.

Invert, put forward, shrink the virtual and the real.

Inversion reduction of u & gt2f real image F

F<u< Real Image 2f Inverted Amplification v & gt2f Slide Projector

U<F |v| > magnifying glass

3. Further understanding of the law:

⑴ u = f is the dividing point between real image and virtual image, positive image and inverted image, and the same side and different side of image.

⑵ u = 2f is the dividing point of image enlargement and reduction.

(3) When the image distance is greater than the object distance, it becomes an enlarged real image (or virtual image), and when the image distance is less than the object distance, it becomes an inverted reduced real image.

(4) into a real image:

5] into a virtual image:

Four, eyes and glasses

1. imaging principle: the light emitted by an object passes through a comprehensive convex lens such as a lens to form an inverted and reduced real image on the retina. Optic nerve cells distributed in the retina are stimulated by light. By transmitting this signal to the brain, people can see this object.

2, myopia and hyperopia correction: myopia should wear a concave lens, hyperopia should wear a convex lens.

Verb (abbreviation for verb) microscope and telescope

1. microscope: there are two groups of lenses at both ends of the microscope barrel, and each group of lenses is equivalent to a convex lens. The convex lens near the eyes is called eyepiece, and the convex lens near the observed object is called objective lens. The light from the observed object becomes an enlarged real image after passing through the objective lens, just like the lens imaging of a projector; The eyepiece is like an ordinary magnifying glass. Enlarge this picture again. After these two magnifications, we can see small objects invisible to the naked eye.

2. Telescope: One kind of telescope is also composed of two groups of convex lenses. The convex lens near the eyes is called eyepiece, and the convex lens near the observed object is called objective lens. Whether we can see an object clearly is very important to the size of the "viewing angle" formed by our eyes. Although the image formed by the objective lens of the telescope is smaller than the original object, it is very close to our eyes, and with the magnifying effect of the eyepiece, the viewing angle can become very large.

The fourth chapter "the change of state" reviews the outline.

I. Temperature

1, definition: temperature indicates the degree of heat and cold of an object.

2. Unit:

① The international system of units adopts thermodynamic temperature.

② The common unit is Celsius (℃): at a standard atmospheric pressure, the temperature of ice-water mixture is 0℃, and the temperature of boiling water is 100℃. They are divided into 100 equal parts, and each equal part is called 1 Celsius. The temperature in a place is -3 degrees Celsius, which is pronounced as-3 degrees Celsius or-3 degrees Celsius.

③ conversion relation T=t+273K

3, measurement-thermometer (commonly used liquid thermometer)

① Thermometer structure: There is a glass bulb below, which contains liquid such as mercury, kerosene and alcohol; There is a thin glass tube with uniform thickness inside, and scales are evenly engraved on the glass tube outside.

(2) Thermometer principle: liquid expands when heated and contracts when cooled to do work.

③ Classification and comparison:

Classified experimental thermometer

Objective to measure the temperature, room temperature and body temperature of objects.

The range is-20℃ ~110℃ ~ 30℃ ~ 50℃ and 35℃ ~ 42℃

The dividing value is 1℃ 1℃ 0. 1℃

The liquid water used is silver, kerosene (red), alcohol (red) and mercury.

There is a special structure necking above the glass bulb.

Usage: Do not shake when using, and do not leave the reading of the object when measuring. You can leave a human reading before use.

(4) The use of common thermometers:

Before use: observe its range and judge whether it is suitable for the temperature of the measured object; And identify the scale value of the thermometer for accurate reading. When in use: all the glass bubbles of the thermometer are immersed in the liquid to be measured, and do not touch the bottom or wall of the container; Immerse the glass bulb of the thermometer in the liquid to be measured for a while, and then read after the pointer of the thermometer is stable; 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.

Exercise: The purpose of enlarging the glass bulb of the thermometer is that the volume changes greatly when the temperature changes, and the purpose of thinning the glass tube above is that the liquid column changes greatly when the liquid volume changes equally. The two measures have the same purpose: accurate reading.

Second, the change of state.

The name of the filling state and the change of endothermic and exothermic;

1, melting and solidification

(1) melting:

Definition: The change from solid to liquid is called melting.

Crystal substances: hypo, ice, timely crystal, amorphous substances: rosin, paraffin glass, asphalt, beeswax.

Salt, alum, sodium chloride, various metals.

Melting image:

Melting characteristics: solid and liquid exist at the same time, absorb heat and keep the temperature unchanged. Melting characteristics: heat absorption, first softening and thinning, and finally becoming liquid.

The temperature keeps rising.

Melting point: the temperature at which a crystal melts.

Melting conditions: (1) reach the melting point. (2) Continue to absorb heat.

② curing:

Definition: The change from liquid to solid is called solidification.

Solidification image:

Solidification characteristics: solid and liquid * * *, exothermic, constant temperature solidification characteristics: exothermic, gradually thickening, becoming sticky, hardening, and finally,

Freezing point: the temperature at which a crystal melts. Solidification, the temperature is decreasing.

The melting point and freezing point of the same substance are the same.

Solidification condition: (1) reaches freezing point. (2) Continue to release heat.

2. Vaporization and liquefaction:

(1) vaporization:

Definition: The change of a substance from liquid to gas is called vaporization.

Definition: Vaporization that can occur at any temperature and only occurs on the surface of liquid is called evaporation.

Influencing factors: (1) temperature of liquid; (2) the surface area of the liquid (3) the airflow on the surface of the liquid.

Function: Evaporation absorbs heat (external or self-heating) and has refrigeration function.

Definition: At a certain temperature, the inside and the surface of the liquid undergo intense vaporization at the same time.

Boiling point: the temperature at which a liquid boils.

Boiling condition: (1) reaches the boiling point. (2) Continue to absorb heat.

Relationship between boiling point and air pressure: The boiling point of all liquids decreases when the air pressure decreases and increases when the air pressure increases.

② Liquefaction: Definition: The process of changing a substance from a gaseous state to a liquid state is called liquefaction.

Methods: (1) Reduce the temperature; (2) compression volume.

Advantages: reduced volume and convenient transportation.

Function: Liquefaction releases heat.

3, sublimation and sublimation:

① Sublimation definition: the process that a substance directly changes from a solid state to a gas state. Substances that absorb heat and sublimate easily are iodine, ice, dry ice, camphor and tungsten.

② Definition of sublimation: the process that a substance directly changes from a gaseous state to a solid state and releases heat.

Exercise: ☆ To make the washed clothes dry as soon as possible, please write four effective methods.

(1) Unfold clothes to increase the contact area with air. (2) Hang clothes in a ventilated place. (3) Hang clothes in the sun or at high temperature. (4) Dehydration of clothes (wringing and drying).

☆ Explain that "Leng Xue is cold before the frost"?

Cold before frost: Only when the outside temperature is low enough can the water vapor in the air release heat and condense into frost, so it is "cold before frost".

Cold after snow: Snow melting is a melting process, which absorbs heat, so it is "cold after snow".