6. Using radiation to investigate stars Flashcards
How is an emission spectra formed?
- 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?
- 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?
- 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?
- 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
- A continuous spectrum
- Crossed by many dark lines
- ∴ complex combination of a continuous emission spectrum and a line absorption spectrum
The dark absorption lines are due to the outer atmosphere of the Sun absorbing only certain wavelengths of radiation
Explain why black lines are present and how info about the composition of a star can be obtained from these lines
- 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
Uhhhh, composition gained from lines as different elements would give off different wavelengths there based on the wavelengths we are shown from the spectra, determines what elements present in the sun
What is black body
An idealized object which absorbs all radiation incident on it. And emits the maximum radiation at each wavelength of the continuous spectrum.
Black body - absorbs all Em radiation that falls on it and no body is a better emitter at the same temperature
The term “black-body” refers to an object that doesn’t reflect any light incident upon it ∴ should appear black. Absorbs 100% of the radiation
Explain the energy distribution in the spectrum of a Black body?
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
Additionally, u can find their extremes of the visible light spectrum and their colour within based on the heat stated
Wien’s law?
Tell me about it
λmax = W/T
λmax = peak wavelength (metres)
W = Wien’s constant (2.9x10-3 metre-kelvin)
T = absolute temperature (°C +273.15 BIG DIFFERENCE)
Helps to find the other values here. In addition, must know how to sketch the shape of the curve for typical graph for this Wien stuff
Intensity of radiation?
Not in data booklet
Tell me about it
Wm-2 = W/m2
Intensity = Power/Surface area
However, that’s only the intensity at its surface
How to gain intensity from a certain distance?
not given in data booklet
I1/I2 = r22/r12
Explanation:
I is just the intensity’s so u can just re-arrange for the intensity’s a certain one from their surface
r is also literally just the radius, so u may have to do some crazy ass re-arranging to gain radius or it tells u and u need to convert it to m. In addition remember to x based on how much further away the planet it.
Don’t forget to square, considering this not in data booklet
Use ur observations please :)
Tell me about multiwave astronomy
Making observations outside visible spectrum to investigate stars
(could be important, 6 marker type shi)
Key features:
- It has all Em-spectrum observations
- X-rays and gamma observe high energy phenomena such as black holes, supernova
- UV observes hot stars
- Visible light observes warmer stars, planets
- IR observes cool stars and the core of our galaxy
- Micro & radio waves observes cold molecular clouds, radiation left over from the Big Bang
^^ Used by telescopes outside atmosphere and inside (I think this for everything)
Ye maybe i’m fucked for this part, might even be everything at this point too :(
Ready to complete…. at what cost?
Absolute life saver, now I didn’t have to go yam just like maths
Hope for the best, BUT AT LEAST U HAVE NOTES READY TO BE COMPLETED LATER!!!
Everything, damn i woulda been cooked
Preciate it
