When you look at people through the door, why do you still see the same people as before

Linear propagation of light, pinhole imaging principle.

A person is illuminated by light, and each luminous point shines in all directions. There is always a small beam of light that goes straight through the door and forms an image on the eyes. Every luminous point of a person will form a corresponding image on the eyes, which is real and projected on the eyes after being reduced in a certain proportion.

Extended data

The law of light propagation:

Light travels in a straight line in the same uniform medium. Aperture imaging, solar eclipse and shadow formation all prove this fact. Aside from the wave nature of light, based on the linear propagation of light, the subject of studying the propagation of light in media and the imaging law of objects is called geometric optics. In geometric optics, geometric lines with arrows represent the propagation direction of light, which is called light.

Geometric optics regards an object as a combination of countless object points (in approximate cases, object points can also be used to represent objects), and the light beam emitted by object points is regarded as a collection of countless geometric rays, and the direction of light rays indicates the transmission direction of light energy.

There are three laws of light propagation in geometrical optics:

The linear propagation law of (1) light has been described above. Geodetic survey is also based on this.

(2) The law of independent propagation of light. When two beams of light meet in the process of propagation, they do not interfere with each other, but continue to spread in their own ways. When two beams of light converge at the same point, the light energy at that point simply adds up.

(3) The laws of reflection and refraction of light. When light meets the interface of two different media on the way, some light is reflected and some light is refracted. Reflected light follows the law of reflection and refracted light follows the law of refraction.

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