2.5 And 2.6 Flashcards
Continuous spectra
Spectra where the radiation is distributed over all frequencies not just specific ranges
Example: blackbody radiation
Is a lightbulb a continuous spectrum ?
Yes
What do you see on the screen of the spectroscope for a continuous spectra ?
A rainbow
Spectra are like what ? (Metaphor )
A bar code that uniquely specify the type of product
Can wavelengths shorter than 400 nm be seen by humans?
No they are in the ultra violet part of the spectrum which is invisible to the human eye
Note: they are shown in purple on the emission spectra
Emission lines
Bright line in a specific location of the spectrum corresponding to emission of light at a certain frequency
Color equals what?
Frequency and wave length
Can emission likes be altered for the same element (or whatever)?
No the intensity can be changed but not the color (frequency or wavelength)
What are emission and absorption lines?
They are characteristic frequencies (wavelengths) at which matter absorbers or emits photons of electromagnetic radiation
What kind of spectrum does the sun have ?
At first it appears to be continuous because of the rainbow but there are dark lines splitting the rainbow because some gases on the surface are being absorbed
Absorption line
Dark line in an otherwise continuous bright spectrum where light within one narrow frequency range has been removed
Absorption lines can be produced in a lab how?
By passing a beam of light from a continuous source through a cool gas
Absorption and emission lines similar ?
Both contain the same information about the gas the absorbption lines occur at the same wavelengths as the emission lines when the gas is heated
Which has more energy a low frequency photon or a high frequency photon?
High frequency photon
Which color has a higher frequency blue or green?
I don’t now
Kirchhoffs laws: rule 1
A luminous solid or liquid or a sufficiently dense gas, emits light of all wavelengths and so produces a continuous spectrum of radiation
Kirchhoffs laws: rule 2
A low density hot gas emits light whose spectrum consists of a series of bright emission lines. These lines are characteristic of the chemical composition of the gas.
Kirchhoffs laws: rule 3
A low density cool gas absorbs certain wavelengths from a continuous spectrum, leaving dark absorption lines in their place, superimposed on the continuous spectrum. These lines are characteristic of the composition of the intervening gas. They occur at precisely the same wavelengths as the emission lines produced by the gas at higher temperatures.
When was helium discovered on earth?
1895