P 6. Using Radiation to investigate stars Flashcards
How is an emission spectra formed?
(4 things)
- Element within gas being heated
- Causes electron to transition and go back down
- Emitting certain wavelengths (coloured lines)
- Creating an emission spectra
How is an absorption spectra formed?
(4 things)
- When emitted radiation passes through a star’s atmosphere
- A line absorption spectrum is produced
- Where atoms absorb certain wavelengths
- Of the electromagnetic spectrum
Explain emission of radiation by an atom?
(6 things)
- Electron in an excited state
- Atom drops back down from 1 energy to another
- Emitting left over energy as a photon
- Change in energy between states = energy of photon
- △E = hc/λ
- Produces lines on spectra at each transition wavelength
Explain absorption of radiation by an atom?
(6 things)
- Electron from a lower state
- Goes up to a higher energy state
- From being heated
- Electron can only absorb energy = a transition in energy states (△E)
- Electron absorbs a photon where △E = hc/λ
- Produces dark lines in continuous spectra of radiation incident on the atom
Tell me about the sun’s spectra
(3 things)
- A continuous spectrum
- Crossed by many dark lines
- ∴ complex combination of a continuous emission spectrum and a line absorption spectrum
Explain the dark absorption lines in the sun’s spectra?
(2 things)
- Due to the outer atmosphere of the sun
- Absorbing only certain wavelengths of radiation
Explain why black lines are present
(6 things)
- Black lines appearing as a packet of quantised energy
- Emitted as photons in all directions
- from the cloud of gas absorbing energy packets
- from a certain source
- in order to move to higher energy states.
- Tries to be stable from emitting packets of quantised energy
How can black lines from a spectra help to find info of the composition of a star?
(3 things, can’t believe u didn’t know what composition is)
- Different elements give off different wavelengths
- Which would show based on the lines position in spectra
- Determines what elements present in the sun
Define the terms “black-body”?
(3 things)
- An object that doesn’t reflect any light incident upon it
- Appears black
- Absorbs 100% of the radiation
Explain the energy distribution in the spectrum of a Black body?
(It’s the graph, 6 steps)
What u can conclude within “that graph”?:
1. Position of peak of curve depends on temperature of the body
2. As temp. increases, the peak wavelength decreases
3. Overall intensity increases as temperature increases
4. At low temperatures, most radiation is IR
5. At higher temperatures, shift towards visible (glows red hot)
6. Higher temperature black body’s have a more defined peak
How do u find the extremes of the visible light spectrum & colour?
By the heat that could be stated on the graph
State Wien’s law?
(2 things)
- The peak wavelength emitted by a hot object
- is inversely proportional to its absolute temperature
What’s the formula for Wien’s law?
λmax = W/T
Define λmax
(Wien’s law)
Peak wavelength (metres)
Define W
(Wien’s law)
Wien’s constant (2.9x10-3 metre-kelvin)
