Definition: an object that can emit light.

Category: Natural light sources (such as sun, fireflies) and artificial light sources (such as electric lights, candles)

Note: The moon and stars are not sources of light

Condition: Light travels in a straight line in the same, uniform, transparent medium

Phenomenon: solar eclipse, lunar eclipse, shadow, laser boring machine, small hole imaging, light spots under trees, etc.

Application: laser collimation, shadow formation, etc.

The velocity in vacuum is about 3.0×10⁸m/s

The speed in water is 3/4 of the vacuum, and the speed in glass is 2/3 of the vacuum

The phenomenon of light hitting the surface of the medium and being reflected back to the original medium

Reflected light, incident light and normal are 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 (it cannot be said that the incident angle is equal to the reflection angle, because there is the incident angle first, and then the reflection angle)

Specular reflection: the reflection surface is smooth, such as a flat mirror, a calm lake surface

Diffuse reflection: the reflection surface is uneven, such as blackboard, curtain, and furry glass

Features: The image formed is a vertical virtual image, the size of the image and object is equal, the connection between the image and object is perpendicular to the mirror, and the distance between the image and object and the mirror is equal.

Application: Imaging, changing the optical path (such as periscope)

Refracted light, incident light and normal in the same plane

Refracted and incident light are separated on both sides of the normal

The refractive angle increases with the increase of the incident angle and decreases with the decrease of the incident angle.

When light is inclined into transparent substances such as water or glass, the refractive angle is smaller than the incident angle; when light is inclined into transparent substances such as water or glass, the refractive angle is greater than the incident angle

From the shore to the water, the water seems to be very shallow; from the water, the things on the shore seem to be getting higher

The chopsticks seem to be "folded" in the water

Mirage.

Rainbow (also a dispersion phenomenon of light)

The phenomenon of sunlight decomposing into seven colors of red, orange, yellow, green, blue, indigo and purple through prisms

Red, green, blue

Convex lens: thick in the middle and thin edges, which converge light

Concave lens: thin middle and thick edges, which have a divergent effect on light

Spindle: A straight line passing through two sphere centers on the lens.

Light center: A special point on the main axis, and the propagation direction of any light passing through this point remains unchanged.

Focus: A convex lens can converge light parallel to the spindle at a point, which is called the real focus of the convex lens; a concave lens can converge the reverse extension line of the refracted light ray of the light parallel to the spindle at a point, which is called the virtual focus of the concave lens.

Focal length: The distance from the focus to the center of light.

Convex lens imaging rules (the relationship between object distance u, image distance v and focal length f):

The principle of the eye's visual object: similar to camera convex lens imaging.

Vision correction: Use concave lens to correct myopia, and use convex lens to correct hyperopia

Definition: The degree of hot and cold of an object

Temperature scale

Function: Measure object temperature

Working principle: made according to the principle of thermal expansion and contraction of liquids

Structure: consists of a glass bubble containing temperature measurement liquid and a thin glass tube with uniform inner diameter

Function: Measuring the temperature of the human body, also known as a medical thermometer

Similarities and similarities with thermometers

molecular

Diffusion phenomenon

Three molecular dynamic theory

Definition: Energy can be transmitted from high-temperature objects to low-temperature objects, or the high-temperature part of the object to low-temperature part. This phenomenon is called heat transfer

Essence: Transfer of energy

Generation conditions: There is a temperature difference

The result of heat transfer: the same temperature

Direction: High temperature → Low temperature

Methods: heat conduction, heat convection, heat radiation

Definition: The amount of energy absorbed or released by an object during reheat transfer is called heat, which is expressed in Q.

Unit: Joule

Heat corresponds to the heat transfer process. Heat cannot be discussed without heat transfer, so we can only say that the object absorbs or releases heat, but we cannot say how much heat the object has.

Definition: The heat absorbed by a certain substance with a unit mass when the temperature rises by 1℃ is called the specific heat capacity of this object, referred to as C for short

Physical significance: The strength of the object's ability to absorb heat and release heat

Calculation formula: c=Q/(m*Δt)

Unit: J/(kg·℃), read as kettle per kilogram of Celsius

Specific heat capacity is a characteristic of substances, and the specific heat capacity of different substances is generally different.

Mass, volume, state, temperature

Heat transfer

acting

Work and heat transfer are equivalent to changing the internal energy of an object

The fuel is burned in the cylinder to generate high-temperature and high-pressure gas. The gas pushes the piston to do work and converts internal energy into mechanical energy.

Working process

Crystal: solid with a certain melting temperature, that is, melting point

Amorphous: solid with no certain melting temperature, that is, melting point

Melting: solid state → liquid state

Solidification: liquid → solid

Vaporization: liquid → gaseous

Liquefaction: gaseous → liquid

Sublimation: solid state → gas state

Ninghua: Gas → Solid