Kids Research Express

The explanation for exact spectral lines for each substance was provided by the  quantum theory . In his 1913 model of the hydrogen atom Niels Bohr showed that the observed series of lines could be explained by assuming that electrons are restricted to atomic orbits in which their orbital angular momentum is an integral multiple of the quantity   h /2π, where  h  is Planck's constant. The integer multiple (e.g., 1, 2, 3 …) of  h /2π is usually called the quantum number and represented by the symbol  n. When an electron changes from an orbit of higher energy (higher angular momentum) to one of lower energy, a  photon  of light energy is emitted whose frequency ν is related to the energy difference Δ E  by the equation ν=Δ E / h. For hydrogen, the frequencies of the spectral lines are given by ν= cR  (1/ n f 2 −1/ n i 2 ) where  c  is the speed of light,  R is the Rydberg constant, and  n f  and  n i  are the final and initial quantum numbers of the electron orbits ( n i  is always

Spectrum, arrangement or display of light or other form of radiation separated according to wavelength, frequency, energy, or some other property. Beams of charged particles can be separated into a spectrum according to mass in a mass spectrometer (see mass spectrograph ). Physicists often find it useful to separate a beam of particles into a spectrum according to their energy. Continuous and Line Spectra Dispersion, the separation of visible light into a spectrum, may be accomplished by means of a prism or a diffraction grating. Each different wavelength or frequency of visible light corresponds to a different color , so that the spectrum appears as a band of colors ranging from violet at the short-wavelength (high-frequency) end of the spectrum through indigo, blue, green, yellow, and orange, to red at the long-wavelength (low-frequency) end of the spectrum. In addition to visible light, other types of electromagnetic radiation may be spread into a spectrum according to