extra questions P7 Flashcards
(28 cards)
Radiation can also be used to kill the bacteria on fresh food. Give one reason why farmers, shop owners or consumers may want food to be treated with radiation.
wider market for farmer
stays fresh longer
The type of radiation emitted from a radioactive source can be identified by comparing the
properties of the radiation to the properties of alpha, beta and gamma radiation.
Describe the properties of alpha, beta and gamma radiation in terms of their:
* penetration through materials
* range in air
* deflection in a magnetic field.
alpha particles
* are least penetrating
* are stopped by paper
* have the shortest range
beta particles
* (some are) stopped by aluminium
* can travel (about) 1 metre in air
* are deflected by a magnetic field
gamma rays
* are the most penetrating
* are stopped by lead
* have the longest range
* are not deflected by a magnetic field
What is a possible risk to health caused by using a radioactive source?
cell damage
Explain why alpha radiation given out by the americium 241 is unlikely to do any harm to
people living in the house
radiation is outside the body
radiation will not reach cells
radiation absorbed by the air
Which part of an atom emits a beta particle
nucleus
What is meant by the term half-life
time taken for activity to decrease to half
What is a gamma ray
electromagnetic wave with high frequency
Between 09:00 and 10:00 the cardboard is produced at the correct constant
thickness. Give a reason for the small variation in count rate.
background radiation
Explain why the radiation source inside the smoke alarm should have a long half-life.
a short half-life means the count rate decreases quickly
until 1.3 half-lives the count rate is above 80 per second
Explain the ideal properties of a radioactive source for use in medical diagnosis.
- short half-life means less damage to cells
- low ionising power
- highly penetrating
- emits gamma radiation
What happens to the structure of an atom when the atom is ionised?
loses/gains (one or more) electron(s)
Name one man-made source of background radiation.
nuclear power
Why is gamma radiation suitable for irradiating food?
Explain the reasons for your choice.
gamma (radiation) will pass through food
long half-life so source does not need frequent
replacement
During the 11 years that Cassini will orbit Saturn, the output from the generators
will decrease.
Explain why.
the rate of decay (of plutonium) decreases
less heat produced
The smoke detector would not work if a radioactive source that emitted only
gamma rays was used.
Why not?
gamma hardly ionises the air
Explain how the paths of the alpha particles were used to develop the nuclear model of the
atom
most alpha particles pass straight through the atom
which shows that the atom is mostly empty space
very few alpha particles are deflected through a large angle
which shows the atom contains a nucleus where the mass of the atom is concentrated
Iodine-131 is used to destroy cancer cells in the human thyroid gland.
Explain why the length of the half-life of iodine-131 is important in this use.
- long enough to destroy cancer cells
- short enough to minimise damage to surrounding tissues
If people drink water contaminated with iodine-131, the iodine-131 builds up in the
thyroid gland. This continues until the thyroid is saturated with iodine-131 and cannot
absorb any more. The radiation emitted from the iodine-131 could cause cancer of
the thyroid.
In Japan, people likely to be drinking water contaminated with iodine-131 were
advised to take tablets containing a non-radioactive isotope of iodine.
Suggest why this advice was given.
- limit the amount of iodine-131 that can be absorbed
- so reducing the risk of cancer (of the thyroid)
Carbon-14 is constantly being made in the atmosphere, yet for most of the last million
years, the amount of carbon-14 in the atmosphere has not changed.
How is this possible?
Carbon-14 decays at the same rate it is made
Sodium chloride solution is known as saline. It is the liquid used in ‘drips’ for seriously-ill
patients. Radioactive sodium chloride, containing the isotope sodium-24, can be used as a
tracer to follow the movement of sodium ions through living organisms.
Give one advantage of using a sodium isotope with a half-life of a few hours compared to
using an isotope with a half-life of: 5 years, 5 seconds
5 years: it doesn’t last as long so may not be as dangerous
5 seconds: would not be there long enough to act as a tracer
Plants use phosphorus compounds to grow. Watering the root system of a plant with
a solution containing a phosphorus-32 compound can help scientists to understand
the growth process. Why are beta particles good for this?
- beta particles can be detected externally
- beta particles can pass through the plant
Why is carbon-14 unsuitable for dating a skeleton believed to be about 150 years
old?
Decay of carbon 14 over 150 years is insignificant
The increased industrial use of radioactive materials is leading to increased amounts of
radioactive waste. Some people suggest that radioactive liquid waste can be mixed with
water and then safely dumped at sea. Do you agree with this suggestion? Explain the
reason for your answer.
For:
- massive dilution of waste
- reduced waste (within a given volume) to insignificant levels
- distant from habitation
The intermediate radionuclides are not important when estimating the age of the rock.
Explain why.
They are relatively short-lived
