2. "No shadow" is actually very simple, that is, many lamps are used to illuminate an object, and the shadow formed by one lamp is covered by the light of another lamp. The shadow formed by another lamp is covered by the light of another lamp.

When you touch a small object on the table with one eye, your hand doesn't touch the small object, but your eyes do tell you that you did. There is no sense of distance when you look at it with one eye, because one eye can only see one dimension, and the distance can only be determined by the cooperation of two eyes. This is because when two eyes look at the same object from different angles, the brain will judge the distance of the object. )

4. The shadow length of telephone poles and buildings can be measured by sunlight at the same time, and then the proportional formula is listed:

Building height pole height

————=————

The building has a long shadow and a long pole.