Lenses are converging and diffusing. Lenses that are thicker in the middle than at the edges, which have the property of collecting a parallel beam of rays at one point, are called collecting lenses. Lenses that are thinner in the middle than at the edges and have the property of scattering a parallel beam of rays are called collecting lenses.
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.