Quantum Phenomena Flashcards
what does the spectrum of light emitted from a heated body depend on?
the material
How can we measure the spectrum of radiation emitted by a hot body?
By directing the light through a prism or a diffraction grating to split the light into its constituent frequencies
Describe the spectrum of a solid or liquid source of light
the spectrum is continuous as the source emits at all frequencies
What does the spectrum of a hot, dense solid object, depends on?
the temperature of the object
Describe the spectrum of a heated gas source of light
the spectrum includes only certain frequencies in the form of sharp lines.
How is the emission line spectrum like a fingerprint?
different atoms emit at different, well-defined frequencies, and unique to a particular element. Spectrographic techniques are widely used as non-invasive methods of studying the constituents of a sample.
How does a cold gas radiate?
a cold gas absorbs radiation
How can the absorption spectrum may be studied?
by shining white light on a sample, and studying the radiation that emerges with a spectrometer (e.g. a diffraction grating or prism).
Describe the absorption spectrum of a cold gas source of light
The light that emerges in this case shows distinct dark lines, corresponding to frequencies absorbed by the material.
What is the spectrum of a heated gas source of light known as?
The spectrum is known as an emission line spectrum, and the lines are called spectral lines.
What is the spectrum of a cold gas source of light known as?
This is known as an absorption line spectrum,
How are the emission and absorption spectrum related?
a gas of atoms of a given species absorbs at the same set of wavelengths as it emits when heated. In the same way as an emission line spectrum, an absorption line spectrum is a signature that allows us to identify elements present in a sample.
What is a blackbody?
It is a perfect absorber, one which absorbs all radiation incident on it, and hence appears black when light is shone on it.
What is modeled as a blackbody?
Stars, and in general dense solid bodies, behave like blackbodies to a good approximation.
What does the spectrum of emission of a blackbody depends on?
its temperature and not on the details of the body.
