Physical knowledge

1) Sunlight can be regarded as parallel light, and telephone poles are relatively thick. When sunlight passes through the edge of a telephone pole, it will diffract, making the width of the shadow of the telephone pole smaller than its diameter. However, because the width of telephone poles is relatively large, it is not obvious to reduce the amount of land.

Similarly, sunlight will diffract wires, but because the wires are too thin and too far from the ground, the shadow of the wires can't be seen clearly because of diffraction.

2) Because incandescent lamps are equivalent to point light sources and fluorescent lamps are equivalent to line light sources, this is similar to the principle of shadowless lamps used in hospitals. Large-area light sources will blur the shadows of objects.