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Physics > Digging up the Past > Flashcards

Digging up the Past Flashcards

1
Q

Current

A

the rate of flow of charge

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2
Q

Potential Difference

A

amount of energy needed to pass through a component per coulomb

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3
Q

Resistance

A

energy used per amp of flow

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4
Q

Large current

A

low resistance

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5
Q

How does the resistance change with size?

A

wider - lower resistance because there’s more area for charge carriers to pass through

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6
Q

Potential Divider circuit

A
  • two different resistors in a circuit

- the terminal potential difference of a supply is divided between series resistors in the ratio of their resistance

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7
Q

Balancing the potential

A

you can find the EMF by finding the balancing point where the potentials are equal

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8
Q

‘Common’ current flow

A

positive to negative (electrons travel the other way)

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9
Q

Electromagnetic spectrum

A

Radio waves, Microwaves, Infra Red, Visible Light, Ultra Violet, X-rays, Gamma Rays

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10
Q

Radio waves end of EM spectrum

A

low frequency, low energy, long wavelength

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11
Q

Gamma rays end of EM spectrum

A

high frequency, high energy, short wavelength

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12
Q

Why do we see light of a particular wavelength?

A

because the sun gives out light and we’ve evolved to see light of this wavelength it gives out

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13
Q

How are x-rays used in archaeology?

A

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

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14
Q

Diffraction

A

the spreading out of a wave as it passes through a gap

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15
Q

How do you get maximum diffraction?

A

if the size of the gap is similar to the wavelength

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16
Q

How can diffraction patterns be used?

A

to identify the structure of atoms and other molecules/objects

17
Q

Why do TEM and SEM work?

A

because electrons can act like waves

18
Q

Electron microscopes (transmission or scanning)

A

beam of electrons scan across to build up an image

19
Q

TEM

A

transmission electron microscope

20
Q

SEM

A

scanning electron microscope

21
Q

How does a TEM work?

A
  • ‘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)
22
Q

Why use electrons in a microscope?

A

their lower wavelength makes it possible to get a resolution a thousand times better than a light microscope

23
Q

How does a SEM work?

A
  • 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
24
Q

Dating Techniques

A
  • Carbon dating
  • Dendrochronology
  • Half life dating
25
Q

Half life dating

A
  • you can work out how much of something radioactive is given off using a Geiger counter
  • then if you know the half life of it you can work out how many half lives it’s gone through to reach the amount you’ve measured and count back how old it is
26
Q

Dendrochronology

A
  • trees grow by adding rings
  • analysing and comparing growth ring patterns of trees and aged wood allows you to know the date cut down so you can count back the age
27
Q

Good conductors

A

low resistivity

28
Q

Good insulators

A

high resistivity

29
Q

Semiconductors

A

in the middle of the resistivity spectrum

30
Q

Metals have

A

free electrons

31
Q

Where are potential divider circuits used?

A

In sensors for street lamps or ovens that stop heating once they reach a certain temperature

32
Q

Diffraction grating

A

a regular array of very narrow lines ruled on transparent plastic/glass this is placed in front of the laser and produces a diffraction pattern

33
Q

Diffraction

A

the spreading out of a wave as it passes through a gap

34
Q

Interference

A

when coherent waves undergo superposition and reinforce or cancel each other out

35
Q

Superposition

A

when two waves interfere and pass through each other either summing or cancelling amplitudes

36
Q

How does an electron gun work

A
  • electrons are ‘boiled’ off a heated filament by thermionic emission
  • they are attracted towards a positive anode accelerated by a potential difference
  • some electrons pass through the vacuum and hit the graphite target
  • others pass through the graphite sheet and diffract before hitting the the graphite target

Physics (12 decks)

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