How do shadows come about?

When light meets an opaque object in the process of traveling in a straight line, the light is blocked by the object and cannot reach the back of the object, forming a dark area similar to the outline of the object behind the object, which is the shadow of the object.

Shadows are formed because light travels in a straight line. The phenomena caused by the linear propagation of light in life include shadow formation, pinhole imaging, solar eclipse and lunar eclipse.

Linear propagation of light;

1. Conditions for straight-line propagation of light: straight-line propagation of light in the same homogeneous medium.

2. The phenomenon that light travels in a straight line: In foggy days, you can see that the beam emitted by car headlights is straight; The beam passing through the forest is straight; In the cinema, you can see that the light beam from the projector is straight. From these phenomena in real life, we can know that light travels along a straight line.

Extended data:

There are three laws of light propagation:

1, the law of straight-line propagation of light.

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 propagate according to their own paths. When two beams of light converge at the same point, the light energy at that point simply adds up.

3. 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.

References:

Baidu Encyclopedia-Shadow