Why is the image of a luminous point in a flat mirror imaginary?

We can see a virtual image. But if we place devices sensitive to light energy (photographic film or just a white screen) at the point where the virtual image is located, then we will not find anything there. The energy of light does not enter this point. Therefore, such an image is called imaginary.

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.