What is the exposure time for physical problems? I'll do it. Come in and have a look.

The definition of exposure, if scientifically explained, is: the intensity of light multiplied by the time of light action. The "light intensity" in the definition refers to the intensity of light illuminating CCD, that is, illuminance (I stands for illuminance, in lux). The "exposure time" in the definition refers to the exposure time (t stands for exposure time, in seconds) when the photosensitive film is irradiated by Love rays. Exposure is measured in lux seconds. Take e as the exposure, and the exposure formula is as follows:

E (exposure) = I (illuminance) ×T (exposure time)

In this problem, the exposure time is the time when the stone moves during shooting; The distance the stone moves is the actual length; So the speed at which the stone moves is

Distance/time = = = 4.0cm/0.02s = 200cm/s = 0.2m/s；/s;

And because the free falling speed of the object = acceleration of gravity (g= 10m/s)* time (t);

So 0.2m/s =10m/s * t; T=0.2s and the acceleration time is 0.2s. 。

When the stone hits the lens, it is about 0.2s of air movement.