Use a light source and a sheet of cardboard with two holes to create a shadow and partial shadow of an opaque object on the screen. Describe the experiment.
The holes in the cardboard are light sources. By changing the distance between the screen, the object and the holes, you can get the shadow and penumbra of various sizes on the screen.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.