What are shadows made of?

Shadows are formed by the straight-line propagation of light.

1, the straight-line propagation of light in uniform medium

It is a basic principle of physics that light travels in a straight line in a uniform medium. When light propagates in the same uniform medium, it does not refract, reflect or scatter, but propagates along a straight line. Therefore, when light meets an opaque object, it will be blocked by the object and spread to the back of the object in a straight line.

2. The formation of shadows

When light meets an opaque object, it cannot pass through the object, but only propagates around it. So there will be a dark area behind the object, which is what we call a shadow. The shape and size of shadow depend on the shape and size of the object and the position and direction of the light source.

3. The application of shadows in daily life

In photography, photographers can use the principle of shadow to create various effects and atmospheres. In architectural design, architects can use the change of shadows to express the three-dimensional sense and aesthetic feeling of buildings. In addition, in drama performance, lighting engineers can use shadow effect to enhance the appeal and expressiveness of the performance.

Correlation between light diffraction and shadow

1, diffraction of light and edge of shadow

Diffraction of light refers to the phenomenon that light will deviate from a straight path when encountering obstacles. When light passes through the edge of an object, it will produce diffraction effect, which will blur the shadow edge. This blurring effect is particularly obvious at the edge of the object, because the light at the edge of the object needs to go through a longer distance to bypass the object and reach the observer's eyes.

2, the distance between the light sources and the size of the shadow

The size of the shadow depends on the distance between the light source and the object. When the light source is far away from the object, the angle of light shining on the object is small, so the shadow of the object will be relatively small.

On the contrary, when the light source is close to the object, the angle of light shining on the object is larger, and the shadow of the object will be larger. This rule is very common in daily life. When walking down the street lamp, the farther away from the street lamp, the smaller the figure will appear.