1. OCR Additional Science
11/04/2017
OCR Additional Science
P4 Radiation for Life
AGAC

2. Equations for this unit (Foundation)
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Equations for this unit (Foundation)
unit 5
unit6

3. the equations needed for this
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unit 5
This slide shows
the equations needed for this
Unit (Higher)
unit6

4. Static Electricity + + - - + - + + + - - - + + - + - -
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Static electricity is when charge “builds up” on an object and then stays “static”. How the charge builds up depends on what materials are used:
Rod becomes
negatively
charged
Rod becomes
positively
charged + + - - + - + + + - - - + + - + - -
It is only the negative charges
-the electrons which move

5. F
11/04/2017
attracted to duster
positive
negative

6. H 11/04/2017 Any three from: Duster has gained electrons
Dust is positively charged
Dust has lost electrons
Opposite charges attract

7. Unlike charges attract
Static Electricity
11/04/2017 + -
Unlike charges attract - -
Like charges repel

8. Van de Graaf generators
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9. Use of static - Photocopiers
11/04/2017 P + 1)
Photocopiers use static electricity. They work by: 1) Copying an ______ of the page onto a ______ plate, 2) Light then causes the charge to ____ away, leaving an “electrostatic impression” of the page, 3) The charges left on the plate ______ small drops of black powder, 4) The powder is transferred from the plate onto the _____, 5) The paper is _____ to “fix” the powder.
image
charged
leak P + 2)
attract
3+4) P +
paper
heated
Words – heated, leak, paper, image, charged, attract

10. Uses of Static – Smoke Precipitators
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Chimney
Negatively charged plates - - - - - -
Positively charged grid + + +

11. Uses and dangers of Static Electricity
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Find out how static electricity is used in the following:
1) Laser printers
2) Paint sprayer
3) Defibrillators
Find out how static electricity is dangerous in the following situations:
1) Fuel pipes
2) Hospitals

12. H 11/04/2017 These need to be opposites positive/negative
negative/positive
attracted
knocked

13. 11/04/2017 F
shock or sparks

14. Wiring a plug 1. Earth wire 4. Live wire 5. Fuse 2. Neutral wire 6.
11/04/2017 1. 2. 3. 4. 5. 6.
Earth wire
Live wire
Fuse
Neutral wire
Cable grip
Insulation
The neutral wire of a plug stays at a potential close to zero relative to the Earth
The live wire of a plug alternates between positive and negative potential relative to the Earth

15. Words – large, harm, safety, melt, live, circuit, fuse
Fuses
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Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____.
safety
live
large
fuse
melt
circuit
harm
Words – large, harm, safety, melt, live, circuit, fuse

16. Words – fuse, fault, metal, surges, touch
Earth wires
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Earth wires are always used if an appliance has a _____ case. If there is a _____ in the appliance, causing the live wire to ______ the case, the current “_______” down the earth wire and the ______ blows.
metal
fault
touch
surges
fuse
Words – fuse, fault, metal, surges, touch

17. Circuit breakers
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Residual Current Circuit Breakers (RCCBs) are often used with fuses. They have some advantages over fuses:
They are safer – they don’t get hot
They react more quickly
They can be switched off for repairs
They are easy to reset
Each RCCB is attached to a certain circuit, so if one switches off you can see which circuit has a fault

18. Resistance V R I Resistance = Voltage (in V) (in ) Current (in A)
Georg Simon Ohm
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Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me.
The resistance of a component can be calculated using Ohm’s Law: V R I
Resistance = Voltage (in V)
(in ) Current (in A)

19. An example question: Ammeter reads 2A A V
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Ammeter reads 2A V A
What is the resistance across this bulb?
Assuming all the bulbs are the same what is the total resistance in this circuit?
Voltmeter reads 10V

20. What is the resistance of these bulbs?
More examples…
11/04/2017 3A 6V
12V 4V 2A 1A 2V 3A
What is the resistance of these bulbs?

21. Resistance Resistance is anything that opposes an electric current.
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Resistance is anything that opposes an electric current.
Resistance (Ohms, ) = Potential Difference (volts, V)
Current (amps, A)
What is the resistance of the following:
A bulb with a voltage of 3V and a current of 1A.
A resistor with a voltage of 12V and a current of 3A
A diode with a voltage of 240V and a current of 40A
A thermistor with a current of 0.5A and a voltage of 10V

22. 11/04/2017 F

23. H
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Break in the circuit
12/1.5 (1) =8

24. Waves- Some definitions…
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1) Amplitude – this is “how high” the wave is:
2) Wavelength () – this is the distance between two corresponding points on the wave and is measured in metres:
3) Frequency – this is how many waves pass by every second and is measured in Hertz (Hz)

25. Some definitions…
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Transverse waves are when the displacement is at right angles to the direction of the wave…
Just pick out one particle and follow its motion
Longitudinal waves are when the displacement is parallel to the direction of the wave…
Just pick out one particle and follow its motion

26. Words – depth, reflected, picture, medium
Ultrasound
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Ultrasound is the region of sound above 20,000Hz – it can’t be heard by humans. It can be used in pre-natal scanning:
How does it work?
Ultrasonic waves are partly _________ at the boundary as they pass from one _______ to another. The time taken for these reflections can be used to measure the _______ of the reflecting surface and this information is used to build up a __________ of the object.
reflected
medium
depth
picture
Words – depth, reflected, picture, medium

27. Other uses of ultrasound
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1) Echo sounding
The ultrasound is reflected from the sea floor.
2) Breaking down kidney stones
Ultrasonic waves break kidney stones into much smaller pieces
3) Cleaning (including teeth)
Ultrasound causes dirt to vibrate dirt off without damaging the object

28. F 11/04/2017 scans to monitor pregnancy break down kidney stones
by vibrating particles
measure blood flow
by measuring frequency change
cleaning instruments
makes dirt particles shake off
treat cancer
using an intense beam aimed at tumour

29. H
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frequency
vibrate
break up

30. The structure of the atom
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ELECTRON – negative, mass nearly nothing
PROTON – positive, same mass as neutron (“1”)
NEUTRON – neutral, same mass as proton (“1”)

31. The structure of the atom
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Particle
Relative Mass
Relative Charge
Proton 1 +1
Neutron
Electron -1
MASS NUMBER = number of protons + number of neutrons He 2 4
SYMBOL
PROTON NUMBER = number of protons (obviously)

32. Introduction to Radioactivity
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Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation:
Radiation
The nucleus is more stable after emitting some radiation – this is called “radioactice decay” and the activity is measured in “Becquerels (Bq)”.

33. Types of radiation
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1) Alpha () – an atom decays into a new atom and emits an alpha particle (2 protons and 2 ______ – the nucleus of a ______ atom)
neutrons
Unstable nucleus
New nucleus
Alpha particle
helium
2) Beta () – an atom decays into a new atom by changing a neutron into a _______ and electron. The fast moving, high energy electron is called a _____ particle.
proton
beta
Beta particle
New nucleus
Unstable nucleus
3) Gamma – after  or  decay surplus ______ is sometimes emitted. This is called gamma radiation and has a very high ______ with short wavelength. The atom is not changed.
energy
frequency
Words – frequency, proton, energy, neutrons, helium, beta
Unstable nucleus
New nucleus
Gamma radiation

34. Changes in Mass and Proton Number
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Alpha decay: Am
241 95 Np α 4 2 +
237 93
Beta decay: Sr 90 38 Y β -1 + 90 39

35. Uses of radioactivity 1 Sterilising medical instruments
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Sterilising medical instruments
Gamma rays can be used to kill and sterilise germs without the need for heating.

36. Uses of radioactivity 2 Beta detector Rollers Paper Beta emitter
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Beta detector
Rollers
Paper
Beta emitter
This is used to make sure the paper/steel is the correct thickness.
The pressure on the rollers is adjusted depending
on how much of the beta is received by the detector

37. Uses of radioactivity 3 Smoke detectors Alpha emitter +ve electrode
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Smoke detectors
Alpha emitter
+ve electrode
-ve electrode
Alarm
Ionised air particles
If smoke enters here a current no longer flows
This sets off an alarm
This involves `a NOT gate
See Unit 6

38. Uses of Radioactivity 4 - Treating Cancer
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High energy gamma radiation can be used to kill cancerous cells. However, care must be taken in order to enure that the gamma radiation does not affect normal tissue as well.
Radioactive iodine can be used to treat thyroid cancer. Iodine is needed by the thyroid so it naturally collects there. Radioactive iodine will then give out beta radiation and kill cancerous cells.

39. 11/04/2017 F / / / /

40. 11/04/2017 F
tracer
decreases
nucleus

41. H 11/04/2017 all of tumour receives the full dose
focussed/directed at/concentrated
all of tumour receives the full dose
Healthy tissue does not
receive the full dose

42. H 11/04/2017 so gamma can reach the surface
low count rate after the blockage

43. Half life
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The decay of radioisotopes can be used to measure the material’s age. The HALF-LIFE of an atom is the time taken for HALF of the radioisotopes in a sample to decay…
= radioisotope
= new atom formed
After 2 half lives another half have decayed (12 altogether)
After 3 half lives another 2 have decayed (14 altogether)
After 1 half life half have decayed (that’s 8)
At start there are 16 radioisotopes

44. A radioactive decay graph
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Count
1 half life
1 half life
1 half life
Time

45. Dating materials using half-lives
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Question: Uranium decays into lead. The half life of uranium is 4,000,000,000 years. A sample of radioactive rock contains 7 times as much lead as it does uranium. Calculate the age of the sample.
Answer: The sample was originally completely uranium…
1 half life later…
1 half life later…
1 half life later… 8 4 8 2 8 1 8
…of the sample was uranium
Now only 4/8 of the uranium remains – the other 4/8 is lead
Now only 2/8 of uranium remains – the other 6/8 is lead
Now only 1/8 of uranium remains – the other 7/8 is lead
So it must have taken 3 half lives for the sample to decay until only 1/8 remained (which means that there is 7 times as much lead). Each half life is 4,000,000,000 years so the sample is 12,000,000,000 years old.

46. An exam question…
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Potassium decays into argon. The half life of potassium is 1.3 billion years. A sample of rock from Mars is found to contain three argon atoms for every atom of potassium. How old is the rock?
(3 marks)
The rock must be 2 half lives old – 2.6 billion years

47. Background Radiation 13% are man-made Radon gas Food Cosmic rays
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13% are man-made
Radon gas
Food
Cosmic rays
Gamma rays
Medical
Nuclear power

48. Uses of radioisotopes - tracers
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A tracer is a small amount of radioactive material used to detect things, e.g. a leak in a pipe:
If there is a
blockage we
know where it is
because there will
be no gamma
reading beyond it
Gamma source
The radiation from the radioactive source is picked up above the ground, enabling the leak in the pipe to be detected.
Tracers can also be used to develop better plant fertilisers and in medicine to detect tumours:

49. Nuclear power stations
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These work by using nuclear fission reactions using uranium:
Nuclear fuel (uranium) is used to boil water in a “heat exchanger”. The steam drives a turbine.

50. 11/04/2017 F
uranium
produce
steam

51. Nuclear fission More neutrons Neutron Uranium or plutonium nucleus
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More neutrons
Neutron
Uranium or plutonium nucleus
Unstable nucleus
New nuclei (e.g. barium and krypton)

52. Chain reactions
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Each fission reaction releases neutrons that are used in further reactions.

53. H
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atom/nucleus
nucleus
neutron
absorb neutrons
fission