| What does each element produce | an individual line spectrum |
| how is a line emission spectrum produced | when an electron is in an excited state in can return to a lower energy level
when it does this it emits a photon
different transitions produce different lines/frequencies of photons |
| How can a line spectrum be observed | using a spectrometer
these can be used to identify the elements presence |
| why are some emission spectrum lines brighter than others | for brighter lines, more electrons are making those transitions per second
there are more photons per second emitted of that specific energy |
| what does the bohr model of the atom propose | an atom has a central positively charged nucleus with electrons in orbits around the nucleus
electron are only allowed in certain fixed orbits (energy levels) and not in the spaces between |
| what is ground state (Eo) | the orbit nearest the nucleus
where the electron has its lowest energy |
| what is meant by an excited state | electrons in higher energy levels |
| what is ionisation level | the energy at which an electron escapes from the electric field of the nucleus
by convention the electron is said to have zero energy when this happens, meaning that the other levels have negative energy levels |
| what does an electron require to move up an energy level | energy |
| what happens when an electron moves down an energy level | the electron gives off energy as a photon |
| how many possible electron jumps are there in these energy levels | six
this corresponds to six lines in the line spectrum |
| what happens to line spectrum if many electrons make the same jump | the spectral line corresponding to that frequency will be bright because many photons are being emitted |
| what kind of spectrum does white light cause | a continuous spectrum when observed through a spectroscope or spectrometer |
| what happens when white light is passed through a coloured filter or a vapour | the frequencies of light corresponding to the energy level transitions for that material are absorbed
this causes black lines on the continuous spectrum |
| what kind of spectrum is produced when the sun is observed through a spectroscope | an absorption spectra |
| how are absorption lines produced | gases present in the outer part of the sun absorb photons of a particular frequency |
| what do absorption lines on an absorption spectra correspond to | emission lines of particular elements
as a result elements present in the atmosphere of the sun can be identified |
| how can we make an electron drop down to a lower energy level | during a process called stimulated emission of radiation
LASER is an example of a device which uses this process |
| how does a laser work | energy supplied to the material the laser is made from causes electrons to become excited
a photon of light stimulates these electrons to drop down to a lower energy level, releasing more photons
these photons have the same frequency, same direction and are in phase with the photon causing their release, so are coherent
more and more photons are emitted, creating the laser beam
part of the beam is reflected back inside the laser
energy is supplied to the laser to cause electrons to go back to a higher energy level. The reflected photons are used to keep the process going. |
| is a laser beam monochromatic? | yes
it is intense at does not spread out in the same way as a point source |
