M7 Topic 1 Part 2: Electromagnetic Spectrum - Spectra Flashcards
what are the types of spectra (2)
continuous
Non-continuous
what types of non continuous spectra are there
emission
absorption
what does a continuous spectra look like
a continuous band of colours (red-violet)
when are continuous spectra observed
incandescent objects (ie galaxies)
what does a emission spectra look like
a black background with coloured bands
how are emission spectra created
When electrons from gases are excited and de-excite releasing energy in the form of electromagnetic waves
What does a absorption spectra look like
coloured background with black bands
how are absorption spectra created(2)
- when continuous spectra(white light) moves through cooler layers of gas, specific frequencies absorbed
- when a continuous spectra(white light) is reflected off objects specific frequencies are absorbed
what are discharge tubes
tubes containing a low-pressure gas through which a current is passed through.
how does a discharge tube work in steps (3)
- the electrical energy excites electrons in the atoms of gas to a higher energy shell/level
- the excited electrons fall back to a lower energy shell/level releasing energy in the form of EM waves in order to get to it’s ground state
- Dependant on the amount of energy released by the electron as it moves to a ground state
how does a flame test work in steps (4)
- the salts introduced to the flame atomise
- the heat energy is absorbed by the electrons going to a higher energy level
- the energy level lowers releasing energy as it moves to lower energy shells in the form of EM waves which if in the visible spectrum will appear as colours
- return to ground state
what is spectroscopy
when a spectrometer is used to observe emission and absorption spectra
how does the spectrometer work
light goes through the prism in the spectroscope revealing the components of the light, which will display a emission or absorption spectra
Why can observing emission and absorption spectra identify the components of a star
Each element (gas) has unique emission and absorption lines, which can be compared to that of a star, to identify elements of the star.
how is abundance of specific elements observed in a stars emission and absorption spectra
the specific elements line will be more defined if in high abundance
how is surface temperature observed
through identifying a blackbody radiation curves peak wavelength
how is peak wavelength calculated
wien’s law: 入ₘₐₓ = b/T
what does each symbol mean in wien’s law and what unit are they measured in (3)
入ₘₐₓ= peak wavelength of the emitted radiation (metres (m)) b= Wien's constant (2.898 x10⁻³ m K) T= the surface temperature of the object (Kelvin (K))
what are the spectral types from hottest to coldest and what are there colours (7)
O = blue B = blue-white A = white F = yellow-white G = yellow K = orange M = red
how can translational velocity to an observer be seen in emission and absorption spectra (2)
The doppler effect- will cause a element’s (gas) emission and absorption spectra to shift:
- To the red side of the spectra (red shift) when moving away from and observer
- To shift to blue side of the spectra (blue shift) when moving closer to an observer
what is the equation for the doppler effect
Δ入/入₀=v/c
what does each symbol mean in the doppler effect equation and what unit are they measured in (4)
Δ入= wavelength shift (metres (m)) 入₀= wavelength of source not moving (metres (m)) v= velocity of shifted source (m/s) c= speed of light (3x10⁸ m/s)
how is rotational velocity of stars observed through emission and absorption spectra
the broadening of absorption and emission lines (defined), the bigger the faster the rotational velocity
why do absorption and emission lines broaden when a star has rotational velocity
the side moving closer to the observer blue shifts, whilst the side moving away redshifts thus making the emission and absorption lines appear broader
how is density observed through emission and absorption spectra
the broadening of absorption and emission lines (undefined), the bigger the more dense
why do absorption and emission lines broaden when stars are more dense
due to the small distance between particles leading to a higher rate of atomic collisions