How do you explain that each substance has its own line spectrum?

Each chemical element has its own line spectrum of emission and absorption, which does not coincide with the spectrum of any other chemical element. Each substance can absorb (emit) light of only certain frequencies. It is by these frequencies that spectral analysis determines the composition of a substance.

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.