When an element is excited by some method, it emits electromagnetic radiations of definite wavelengths. The arrangement of these wavelengths in order of increasing wavelength is called emission spectrum of the element. (as per my book) But, the definition of absorption spectrum, I don't understand.It goes like this: When a beam of continuous light is passed through a tube containing vapors or solution of the substance and the transmitted light is analysed with the help of a spectrometer , it is observed that the spectrum obtained contains a number of dark lines in otherwise continous spectrum. These dark lines appear due to the absorption of radiations of corresponding wavelengths by the substance. The dark lines in the absorption spectrum of a substance appear at the same position as the bright lines in the emission spectrum of the substance. What does the definition mean. Specially, explain the underlined sentences. Thanks in advance for help.