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Do you remember the content of A-level Physics regarding spectra? 👩🏫
Continuous spectra
- The spectrum of light from a filament lamp is a continuous spectrum of colour from deep violet at about 350nm to deep red at about 650nm.
- The most intense part of the spectrum depends on the temperature of the light source.
- The hotter the light source, the shorter the wavelength of the brightest part of the spectrum.
- By measuring the wavelength of the brightest part of the continuous spectrum, we can therefore measure the temperature of the light source.
- Is the superimposed image of both absorption and emission spectra
- Contain no observable gaps
- Contain all the wavelengths of a given range
- Rainbow and black body radiation
Line emission spectra
- A glowing gas in a vapour lamp or a discharge tube emits light at specific wavelengths so its spectrum consists of narrow vertical lines of different colours.
- The wavelengths of the lines are characteristic of the chemical element that produced the light.
- If a glowing gas contains more than one element, the elements in the gas can be identified by observing its line spectrum.
- Huge gaps between lines
- Contain only a few wavelengths
Line absorption spectra
- A line absorption spectrum is a continuous spectrum with narrow dark lines at certain wavelengths. For example, if the spectrum of light from a filament lamp is observed after passing it through a glowing gas, thin dark vertical lines are observed superimposed on the continuous spectrum.
- The pattern of the dark lines is due to the elements in the glowing gas. These elements absorb light of the same wavelengths they can emit at so the transmitted light is missing these wavelengths.
- The atoms of the glowing gas that absorb light then emit the light subsequently but not necessarily in the same direction as the transmitted light.
References:
https://pediaa.com/difference-between-absorption-and-emission-spectra/
https://pediaa.com/difference-between-continuous-spectrum-and-line-spectrum/
https://www.researchgate.net/figure/Continuous-spectrum-and-two-types-of-line-spectra_fig4_235259164
This is the end of the topic!
Drafted by Cherry (Chemistry)