Digging up the Past Flashcards
Current
the rate of flow of charge
Potential Difference
amount of energy needed to pass through a component per coulomb
Resistance
energy used per amp of flow
Large current
low resistance
How does the resistance change with size?
wider - lower resistance because there’s more area for charge carriers to pass through
Potential Divider circuit
- two different resistors in a circuit
- the terminal potential difference of a supply is divided between series resistors in the ratio of their resistance
Balancing the potential
you can find the EMF by finding the balancing point where the potentials are equal
‘Common’ current flow
positive to negative (electrons travel the other way)
Electromagnetic spectrum
Radio waves, Microwaves, Infra Red, Visible Light, Ultra Violet, X-rays, Gamma Rays
Radio waves end of EM spectrum
low frequency, low energy, long wavelength
Gamma rays end of EM spectrum
high frequency, high energy, short wavelength
Why do we see light of a particular wavelength?
because the sun gives out light and we’ve evolved to see light of this wavelength it gives out
How are x-rays used in archaeology?
they can be used to find out the content of artefacts, to look at things such as a mummy without destroying or damaging it, they can be used to assess the condition of archaeological finds
Diffraction
the spreading out of a wave as it passes through a gap
How do you get maximum diffraction?
if the size of the gap is similar to the wavelength
How can diffraction patterns be used?
to identify the structure of atoms and other molecules/objects
Why do TEM and SEM work?
because electrons can act like waves
Electron microscopes (transmission or scanning)
beam of electrons scan across to build up an image
TEM
transmission electron microscope
SEM
scanning electron microscope
How does a TEM work?
- ‘light’ source at top of microscope emits electrons
- they travel through a vacuum in the column of the microscope
- electromagnetic lenses focus the electrons into a thin beam which travels through the specimen
- some electrons scatter and ‘disappear’ while the rest hit a fluorescent screen which creates a shadow image (varied darkness due to varied density)
Why use electrons in a microscope?
their lower wavelength makes it possible to get a resolution a thousand times better than a light microscope
How does a SEM work?
- electrons fired into a vacuum, are accelerated but the electron beam bounces off specimen and the image is formed of the reflected electrons shown on a screen
- the electron beam is repeatedly swept across the specimen to build the image in detail
Dating Techniques
- Carbon dating
- Dendrochronology
- Half life dating
