Why can a high-speed rotating fan see every blade clearly when facing the light at night?

The coolness in summer sometimes reduces people's work efficiency. It is also very good to have an electric fan or air conditioner to reduce the temperature of our environment. Many people have found high-speed rotating fans. Why can they see every fan at night? That's because our eyes want to see the reflected light of objects, and the light generated by electric lamps is discontinuous, so we can see the leaves clearly in the light at night. Let's find out why.

First of all, we know that everything our eyes see enters our eyes through the reflection of light. Without a light source, it is difficult for us to see things clearly. When the fan rotates rapidly during the day, it is difficult for us to see its blades clearly. That's because the frequency that our eyes see is not the same as the frequency at which the leaves rotate under continuous sunlight, so it is difficult for us to see the rotating leaves clearly, only a circular trajectory can be seen. Then the light source at night is the energy-saving lamp above us. As an intermittent light source, this kind of light is invisible to us. If we shoot this light with a high-speed camera, we can see that it is an intermittent light, but our eyes can't feel it.

It is the light source that makes the blades of the electric fan look like a plane in the sun. At night, due to the frequency of alternating current, the light source is discontinuous. At night, when we see the rotating blade facing the light, we can clearly see that the light is hitting the blade at a similar frequency. That's why we can see the leaves at night, not only at night, but also during the day. We can also see the leaves clearly with a camera with a powerful instantaneous photo function.

So sometimes our eyes? Cheating? For ourselves, we should treat interesting scientific events around us with a scientific attitude, so that our life will not be boring.