GENERAL KNOWLEDGE

Detailed explanation-1: -White light (what we call visible or optical light) can be split up into its constituent colors easily and with a familiar result: the rainbow. All we have to do is use a slit to focus a narrow beam of the light at a prism.

Detailed explanation-2: -The spectrum of a galaxy will represent the total light coming from those objects that are contributing the most to the light of the galaxy. These objects will be those that far outnumber other objects, or are the most luminous (red giants), or both.

Detailed explanation-3: -Spectrographs. Astronomers use spectrographs attached to telescopes to view the spectral lines of stars and other celestial objects. A spectrograph combines either a prism or diffraction grating to spread the light from a source into its spectrum. It then has a detector, usually a CCD, to record the spectrum.

Detailed explanation-4: -Light from a star can be separated into its component colors to form a spectrum. The spectrum reveals details in the brightness of different colors of starlight that are not visible to the naked eye. Detectors in the telescope can measure the precise brightness of individual wavelengths.