Digging up the Past

Question 1

Current

Answer 1

the rate of flow of charge

Question 2

Potential Difference

Answer 2

amount of energy needed to pass through a component per coulomb

Question 3

Resistance

Answer 3

energy used per amp of flow

Question 4

Large current

Answer 4

low resistance

Question 5

How does the resistance change with size?

Answer 5

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

Question 6

Potential Divider circuit

Answer 6

• two different resistors in a circuit

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

Question 7

Balancing the potential

Answer 7

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

Question 8

‘Common’ current flow

Answer 8

positive to negative (electrons travel the other way)

Question 9

Electromagnetic spectrum

Answer 9

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

Question 10

Radio waves end of EM spectrum

Answer 10

low frequency, low energy, long wavelength

Question 11

Gamma rays end of EM spectrum

Answer 11

high frequency, high energy, short wavelength

Question 12

Why do we see light of a particular wavelength?

Answer 12

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

Question 13

How are x-rays used in archaeology?

Answer 13

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

Question 14

Diffraction

Answer 14

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

Question 15

How do you get maximum diffraction?

Answer 15

if the size of the gap is similar to the wavelength

Question 16

How can diffraction patterns be used?

Answer 16

to identify the structure of atoms and other molecules/objects

Question 17

Why do TEM and SEM work?

Answer 17

because electrons can act like waves

Question 18

Electron microscopes (transmission or scanning)

Answer 18

beam of electrons scan across to build up an image

Question 19

TEM

Answer 19

transmission electron microscope

Question 20

SEM

Answer 20

scanning electron microscope

Question 21

How does a TEM work?

Answer 21

• ‘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)

Question 22

Why use electrons in a microscope?

Answer 22

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

Question 23

How does a SEM work?

Answer 23

• 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

Question 24

Dating Techniques

Answer 24

• Carbon dating
• Dendrochronology
• Half life dating

Question 25

Half life dating

Answer 25

• 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

Question 26

Dendrochronology

Answer 26

• 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

Question 27

Good conductors

Answer 27

low resistivity

Question 28

Good insulators

Answer 28

high resistivity

Question 29

Semiconductors

Answer 29

in the middle of the resistivity spectrum

Question 30

Metals have

Answer 30

free electrons

Question 31

Where are potential divider circuits used?

Answer 31

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

Question 32

Diffraction grating

Answer 32

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

Question 33

Diffraction

Answer 33

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

Question 34

Interference

Answer 34

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

Question 35

Superposition

Answer 35

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

Question 36

How does an electron gun work

Answer 36

• 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