1. Nature of light
a. Illuminant: An object, such as the sun or an electric lamp itself, is called a luminous body.
b. Rectilinear propagation of light: the light of a luminous body diverges in all directions. The scattered light travels in a straight line in the absence of obstacles, this phenomenon is called rectilinear propagation of light.
c. Propagation velocity of light: the propagation velocity of light in the air is about 299790km/s.
2. The role of spheres
a. Convex lens: the lens with thicker center than the edge is called a convex lens. It has the function of converging the light.
b. Concave lens: the lens with thinner center than the edge is called a concave lens. It has the function of dispersing the light.
3. Reflection of light
Reflection: The surface of the water shines, the sparkle of the glass of the walking car is the rebound of the sun, and the bounce of light is called reflection.
Reflection law: The incident ray and the normal line are in the same plane, and the incident angle is equal to the reflection angle.
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