How are emission lines produced?
When electrons de-excite they emit photons of discrete frequencies.
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What causes discrete emission lines?
Electrons are in quantised energy levels.
When electrons de-excite between these energy levels, only photons of certain frequencies are emitted.
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What causes absorption lines?
When a continuous spectrum of light is passed through a gas, discrete wavelengths of light are absorbed to excite electrons in the gas.
This results in dark lines corresponding to the absorbed wavelengths in the line absorption spectra.
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State the equation linking photon energy (E), frequency (f) and the different between energy levels E1 and E2.
E = photon energy (J)
h = Plank's constant = 6.63 x 10-34 (J s)
f = frequency (Hz)
ΔE = difference between energy levels (J)
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Do emission spectra of the same element always look the same?
Yes.
Each element has it's own set of discrete energy levels which correspond to the wavelengths of light emitted.
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What is a continuous spectrum of light?
Light emitted across a continuous range of wavelengths.
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