1. Light source: An object that can emit light is called a light source. Light sources can be divided into 1, cold light sources (jellyfish, energy-saving lamps) and hot light sources (flashlight, sun); 2. Natural light sources (jellyfish, sun) and artificial light sources (light bulbs, flashlights); 3. Biological light sources (jellyfish, axe fish) and abiotic light sources (sun, light bulbs)

Second, the spread of light.

1. Light travels in a straight line in the same uniform medium;

2, the application of straight-line propagation of light:

(1) pinhole imaging: the shape of the image has nothing to do with the shape of the pinhole, like an inverted real image (the spot in the shade is the image of the sun).

(2) Straight line: laser collimation (directional tunnel); Assemble the whole team; Shoot and aim;

(3) Restrict the line of sight: sit in the well and watch the sky (it is required to make an optical diagram of the frog's field of vision with or without water); A leaf is blind;

(4) the formation of shadow: shadow; Eclipse, eclipse (it is required to know that the moon is in the middle during the eclipse; The earth is in the middle during the eclipse)

3. Light: straight lines with arrows are often used to indicate the trajectory and direction of light;

Third, the speed of light.

1, the speed of light in vacuum is the fastest in the universe;

2. In the calculation, the speed of light in vacuum or air is c = 3×108m/s;

3. The speed of light is about 3/4c in water and 2/3c in glass;

4. Light year: it is the distance that light travels in one year, and the light year is the unit of length; 1 light year ≈ 9.46×1015m;

Note: Sound propagates fastest in solid, followed by liquid, slowest in gas and not in vacuum; Light travels fastest in vacuum, followed by air, and slowest in transparent liquids and solids (and vice versa). The speed of light is much faster than the speed of sound (if lightning is seen before thunder is heard, the time of sound propagation cannot be ignored in the 100m competition, but the time of light propagation can be ignored).

Fourth, the reflection of light:

1. When light strikes the surface of an object, some light will be reflected back by the object. This phenomenon is called light reflection.

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

3. Law of reflection: In the phenomenon of reflection, reflected light, incident light and normal are all in the same plane; Reflected light and incident light are separated on both sides of the normal; The reflection angle is equal to the incident angle.

(1), normal: a straight line perpendicular to the reflecting surface made through the incident point of light;

(2) Incident angle: the angle between incident light and normal; Reflection angle: the angle between the normal ray and the normal. (The incident light forms an angle θ with the mirror surface, the incident angle is 90-θ, and the reflection angle is 90-θ).

(3) There is a causal relationship between the incident angle and the reflection angle, and the reflection angle always changes with the change of the incident angle, so we can only say that the reflection angle is equal to the incident angle, but we can't say that the incident angle is equal to the reflection angle. (The mirror rotates θ, and the reflected light rotates 2θ)

(4) What is the incident angle and reflection angle equal to at normal incidence? A: At normal incidence, the incident angle is 0 degrees and the reflection angle is equal to 0 degrees.

4. In the reflection phenomenon, the light path is reversible (eyes look at each other).

5. Draw a general light path diagram by using the reflection law of light (required):

(1), determine the incident (reflection) point: the incident (reflection) point is the intersection of incident light and reflection surface or reflected light and incident light.

(2) Make a normal according to the fact that the normal is perpendicular to the reflecting surface.

(3) Draw incident light or reflected light according to the fact that the reflection angle is equal to the incident angle.

5. Two kinds of reflection: specular reflection and diffuse reflection.

(1) Specular reflection: When parallel light hits a smooth reflecting surface, the reflected light still reflects out in parallel;

(2) Diffuse reflection: When parallel light hits the rough reflecting surface, the reflected light will be reflected in all directions;

(3) Similarities between specular reflection and diffuse reflection: both are reflection phenomena, and both obey the law of reflection; The difference is that the reflective surfaces are different (one is smooth and the other is rough), and the incident light in one direction, the reflected light reflected by the mirror only shines in one direction (glare); And diffuse reflection is emitted in all directions; In rainy days, walk towards the light in the dark, and the backlight should be in a bright place because of the specular reflection of accumulated water and the diffuse reflection of the ground. The film screen is rough, and when the blackboard is rough, the light is diffused everywhere, and the "reflection" on the blackboard is specular reflection. )

Five, plane mirror imaging

1, the characteristics of plane mirror imaging: Like a virtual image, the image and the object are symmetrical about the mirror surface (the image and the object are equal in size, the connecting line between the corresponding points of the image and the object is perpendicular to the mirror surface, and the distance to the mirror surface is equal; The image is the same as the object up and down, but the left and right are opposite (Byakki Smoker's left hand is a person's right hand, and the time to look at the clock in the mirror depends on the reverse side of the paper. When the object is far away from the mirror and near the mirror, the size of the mirror remains the same, but for people who are at the same distance from the mirror and near the mirror, the size of the mirror is twice the distance).

2. Reasons for the formation of reflection in water: A calm water surface is like a flat mirror, which can be imaged (moon in water, flowers in the mirror); For each point of a physical object, the distance between the image point and the object point in the water is equal. Trees and houses are at different distances from the water. The closer the point is to the water surface, the closer the image is to the water surface. An image composed of countless points is a reflection on the water. How high an object is from the water surface is how far it is from the water surface, regardless of the water depth.

3. The reason why the plane mirror becomes a virtual image: the reflected light of the light emitted by the object on the plane mirror will not converge, and the other is divergent. The image formed by the intersection of the reverse extension lines of these rays (dotted lines when drawing) cannot be presented on the screen, and can only be observed by human eyes, so it is called a virtual image (not formed by the convergence of actual rays).

Note: The light entering the eyes does not come from the image point, but is reflected light. It is required to make light path diagrams (objects, images, reflected light and incident light) by using the plane mirror imaging law (images and objects are symmetrical about the mirror surface) and the plane mirror imaging principle (after light from the same object point is reflected, the reverse extension line of the reflected light passes through the image point);

Six, convex mirror and concave mirror.

1, the outer surface of the ball is called convex mirror, and the inner surface of the ball is called concave mirror;

2. The convex mirror has a divergent effect on light, which can increase the field of vision (rearview mirror on the car); Concave mirror can converge light (solar cooker, using reversible light path as flashlight).

Seven, the refraction of light

1. When light obliquely enters another medium from one medium, the propagation direction is deflected.

2. Light propagates in the same medium. When the medium is uneven, the propagation direction of light will also change.

3. Refraction angle: the angle between the refracted light and the normal.

Eight, the law of refraction of light

1, in the refraction of light, three lines * * * plane, the normal is in the middle.

2. When light obliquely enters water or other media from the air, the refracted light deflects to the normal direction; When light enters the air obliquely from water or other media, the refracted light is far away from the normal (it is required to draw the optical path diagram of refracted light and incident light).

3. When shooting sideways, the angle in the air is always large; At normal incidence, the refraction angle and incident angle are equal to 0, and the propagation direction of light remains unchanged.

4. The refraction angle increases with the increase of incident angle.

5. When light touches the interface between two media, reflection and refraction occur simultaneously.

6. The optical path is reversible in the refraction of light.

9. Refraction of light and its application

1. Examples related to the refraction of light in life: the position of fish in water looks higher than the actual position (the fish is actually below and behind the position); Due to the refraction of light, the pool water looks shallower than it really is; People in the water look at the scenery on the shore higher than the actual position; In summer, the position of stars in the sky is higher than the actual position of stars; Looking at the pen through the thick glass, the pen holder seems to be in the wrong position; Chopsticks are placed obliquely in the water, as if they are bent upward; (Optical diagram required)

2. People use the refraction of light to see that the image of an object in water is a virtual image (the intersection of the opposite extension lines of refracted light).

X. light scattering:

1. After sunlight passes through the prism, it is decomposed into seven colors: red, orange, yellow-green, blue, indigo and purple. This phenomenon is called dispersion.

2. White light is polychromatic light mixed with various colors;

3. The rainbow on the horizon is the dispersion phenomenon of light;

4. The three primary colors of color light are: red, green and blue; Other colors can be mixed with these three colors, and white light can be mixed with red, green and blue. There is no black light in the world; The three primary colors of pigment are magenta, cyan and yellow, and the mixture of the three primary colors is black;

5. The color of transparent body is determined by the color light it passes through (what color passes through what color light); No, the color of transparent body is determined by the color light it reflects (what color reflects what color light, absorbs other colors, white objects emit all colors of light, and black absorbs all colors of light).

Example: A piece of white paper is painted with a red horse, green grass, red flowers and black stones. Now, when you look at this painting in a dark room with green light, you will see a black horse, a black stone and a black flower on green paper, but you can't see the grass (grass and paper are both green).

Eleven, invisible light:

1, solar spectrum: the seven colors of red, orange, yellow, green, blue, indigo and purple are arranged in sequence, which is the solar spectrum;

(From left to right, its wavelength gradually decreases; Scattering gradually increases; The sun is red at night, blue on sunny days, and the fog lights of cars are yellow.

2, infrared: infrared is located outside the red light, invisible to the human eye;

(1) All objects can emit infrared rays, and the higher the temperature, the more infrared rays are radiated; (Night vision goggles for war)

(2) The infrared ray has strong ability to penetrate clouds (remote detection)

(3) The main performance of infrared ray is its strong thermal effect; (heating)

3. ultraviolet light: it is located outside the purple light in the spectrum and is invisible to the human eye;

(1) The main feature of ultraviolet ray is its strong chemical action; (disinfection, sterilization)

(2) The physiological function of ultraviolet rays promotes the synthesis of vitamin D (children spend more time in the sun), but excessive ultraviolet rays are harmful to human body (ozone can absorb ultraviolet rays, so it is necessary to protect the ozone layer).

(3) fluorescence; (check money)

(4) Natural ultraviolet rays on the earth come from the sun, and the ozone layer prevents ultraviolet rays from entering the earth;

The above is the focus of the current physics book, and other focuses with lenses are old books.