Atoms Test - 4

White light gets refracted into different colours, each of different wavelength when passed through a prism or diffraction grating. This process is called dispersion.

The continuous spectrum is obtained from Sun, incandascent solids and red hot gases at high pressure.

Since the energy states of an element are definite, the atoms of that element emit light of some particular wavelength only. Every element has different atomic spectrum and so this emission spectrum can be used to find the material composition.

If a gas, liquid or transparent solid substance is placed between a light source giving a continuous spectrum, the substance absorbs certain part of the spectrum giving few dark lines or bands in these areas.This is called absorption spectrum.

The spectrum of light emitted by a luminous source is called emission spectrum of that source. Hydrogen gas when heated to a high temperature, splits up into hydrogen atoms.  These atoms initially absorb energy and move on to higher energy levels. After a small duration, they emit different amounts of energy and return back to their older level. This produces large number of lines in the atomic spectrum of hydrogen. Each line corresponds to light of specific wavelengths. 

Each element absorbs different amount of energy depending on the number of electrons it has and the electrons move to a higher energy level. After a short duration, these electrons come down, emitting light of definite wavelength and definite frequency. The number of electrons decides the wavelength and frequency of light emitted. Hence emission light spectra of different elements is different.

This behaviour of hydrogen atoms was explained beautifully by Bohr. But it couldnt be applied for complex atoms. Bohr couldnt understand why spectral lines of some atoms were further split into multiple lines in presence of magnetic field. It was further solved by understanding that each electron had a tiny magnetic effect. This was well explained by the Zeeman effect.