Question
Explain in brief about emission spectrum and absorption spectrum.
✓
Answer
• Emission Spectrum
→Each element has a characteristic spectrum of radiation emitted by it.
→When an atomic gas or vapour is excited at low pressure by passing an electric current through it, the emitted radiation has a spectrum which contains certain specific wavelengths.
→A spectrum of this type is called emission line spectrum and it consists of bright lines on a dark background.
→The spectrum emitted by atomic hydrogen is shown in the figure.
• Absorption spectrum :
→When white light is passed through an atomic gas, certain types of wavelengths are absorbed.
→An atom absorbs only those wavelengths that takes it from one excited state to another excited state.
→As a result if the emitted light is analyzed with a spectrometer, a dark line is seen instead of the wavelength that has been absorbed.
→Thus, this is called the absorption spectrum of the material of the gas.
→Each element has a characteristic spectrum of radiation emitted by it.
→When an atomic gas or vapour is excited at low pressure by passing an electric current through it, the emitted radiation has a spectrum which contains certain specific wavelengths.
→A spectrum of this type is called emission line spectrum and it consists of bright lines on a dark background.
→The spectrum emitted by atomic hydrogen is shown in the figure.
• Absorption spectrum :
→When white light is passed through an atomic gas, certain types of wavelengths are absorbed.
→An atom absorbs only those wavelengths that takes it from one excited state to another excited state.
→As a result if the emitted light is analyzed with a spectrometer, a dark line is seen instead of the wavelength that has been absorbed.
→Thus, this is called the absorption spectrum of the material of the gas.
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