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Science 10 - Radiation Review
1. The word RADIATION is a general, unspecific term that can refer to sever types of things.
ELECTROMAGNETIC radiation includes visible light, X-rays, and heat.
2. VISIBLE light consists of all the colours of the rainbow (R O Y G B I V).
3. A SUNBURN is the effect of electromagnetic radiation (specifically ULTRAVIOLET light) on the skin.
4. Invisible X-RAYS can be used to make photographs to show if bones are broken.
8. Radio waves have LONG wavelengths and LOW frequencies. On the other end of the spectrum, X-rays and
Gamma Rays have short wavelengths and high frequencies. Red light has a longer wavelength than Blue
light. Except for visible light, all electromagnetic radiation is invisible.
9. The higher the frequency of the radiation, the greater its amount of ENERGY. This is why X Rays and
Gamma rays are dangerous to living things: they have enough energy to damage cells.
10. Atoms that emit radiation from their nuclei are said to be RADIOACTIVE. When an unstable nucleus emits
radiation, it is said to undergo radioactive DECAY.
11. There are three types of radiations that radioactive nuclei normally emit: ALPHA radiation, BETA radiation,
and GAMMA radiation. Radiation can be detected using an instrument called a GEIGER Counter.
12. Alpha particles are like a HELIUM nucleus. They consist of two PROTONS and two NEUTRONS. They are
the heaviest but least penetrating.
13. Beta particles are like high energy ELECTRONS. When a nucleus undergoes beta decay, a neutron is
converted to a PROTON and an ELECTRON. The ELECTRON is emitted as a beta particle, but the
PROTON remains in the nucleus. The atomic number of an atom undergoing beta decay, therefore, will
always INCREASE by one. The MASS number will not change.
14. GAMMA rays have no mass and travel at the speed of LIGHT. They are a form of ELECTROMAGNETIC
radiation. They are the MOST penetrating.
15. The sum of the number of protons and neutrons in the nucleus is called the MASS number.
16. All atoms of the same element have the same ATOMIC number, but can have different MASS numbers.
Atoms of the same element that have different mass numbers are called ISOTOPES.
17. Carbon-13 has 6 protons and 7 neutrons. The "13" stands for the MASS number. Carbon-14 has 6 protons
and 8 neutrons.
18. The type of radioactive decay that does not give off a particle is called GAMMA decay. After the nucleus has
undergone this sort of decay, however, it is more STABLE.
19. Alpha and beta decay always results in new type of NUCLEUS being formed. A new type of nucleus being
formed is called a NUCLEAR TRANSMUTATION.
20. When a nucleus goes through alpha decay, its mass number DECREASES by FOUR units.
21. The ACTIVITY of a sample is the number of nuclei that undergo radioactive decay per second. It is
measured in units called BECQUERELS (Bq).
22. The activity of a sample of a radioactive isotope DECREASES with time, since there are less nuclei left in
the sample to decay. However, the rate of decay for any radioactive isotope is CONSTANT.
23. The time that it takes for 50% of the nuclei in a radioactive sample to decay is called HALF-LIFE. This time
is the SAME regardless of the starting amount of the radioactive isotope. For example, if you start with 96
grams of radioactive Thorium (which has a half-life of 24 days), after 24 days you would have 48 grams left,
after 48 days you would have 24 grams left, after 72 days (which is equal to three half-lifes) you would have
12 grams left, and so on.
24. The total amount of radiation that strikes you from all sources outside and inside you is known as the
NATURAL BACKGROUND radiation, and there is very little that you can do about it.
25. Alpha, beta, gamma, X-rays, and ultraviolet radiation are all very HAZARDOUS, as they can knock electrons
off of atoms (forming charged atoms called ions). For this reason, these types of radiation are called
IONIZING radiation.
26. Ionizing radiation can cause changes in your DNA! These changes are called MUTATIONS, which can
cause normal cell division to go "out of control" and thus cause CANCER.
27. The effects of ionizing radiation doses is measured using the GRAY (which measures the amount of energy
that the radiating transfers) and the SIEVERT (which measures the effect of radiation on living things). One
gray of beta or gamma radiation is equivalent 1 Sv in its effect on living things, but one gray of alpha
radiation is equal to 20 Sv. You should get exposed to no more than 0.005 Sv of radiation per year.
28. To protect yourself from radiation, use sunscreen to block UV rays, and keep your distance from ionizing
radiation, as well as minimize the amount of TIME you spend in the presence of radiation.
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29. Radiation is useful in medicine, as X-RAYS can be used to show broken bones or decaying teeth. The
pictures take using X-rays are called RADIOGRAPHS. Bones appear lighter on radiographs because X-rays
are ABSORBED by bones before they can expose the film.
30. Radioactive isotopes can be used to track the flow of blood through a patient to show, for example, a
clogged coronary artery. The radioactive isotopes used emit GAMMA rays that can be detected using
special cameras..
31. Radiation is used to treat certain disorders of the THYROID gland (a gland near the base of your neck that
releases the hormone thyroxin, which speeds up cell metabolism). Radioactive iodine-131 is injected into
the person. It travels to the thyroid gland, where it emits BETA particle to destroy part of the overactive
thyroid gland.
32. Some CANCERS can be treated using radiation. For example, bone cancer can be treated by injecting
radioactive strontium-89 into the patient's blood. Bones absorb the strontium just like they normally would
calcium, and the beta emissions from the strontium-89 kill the cancer cells. Radiation "guns" that emit Xrays or gamma rays can also be aimed right at the tumor to kill the cancer. Unfortunately, radiation
treatment also effects HEALTHY cells, and so patients often become very sick during the course of
treatment.
33. EINSTEIN showed that mass and energy are related by the famous equation E = mc 2, where "c" stands for
the speed of LIGHT. This equation says that a little bit of MASS can be converted into a lot of ENERGY.
34. When a large nucleus decays into two or more pieces, this is called nuclear FISSION. Uranium, for
example, can be split by firing NEUTRONS at uranium nuclei. In the process, some of the mass of the
uranium's decay products is converted into large amounts of ENERGY. The fission of uranium also
produces more neutrons that can go on to cause similar fission reactions to take place in surrounding cells.
This is called a CHAIN REACTION, because some of the products of the reaction go on to cause more
reactions to occur. Fission reactions like this one are used to power nuclear REACTORS (and atomic
BOMBS). To get a chain reaction to proceed, you need a certain mass of fissionable material. This amount
is called the CRITICAL mass. If there is enough of the fissionable material around, the chain reaction can
be UNCONTROLLABLE, resulting in an explosion.
35. A nuclear reactor uses a CONTROLLED fission chain reaction to produce energy. In a reactor,
MODERATORS are used to slow down neutrons so that they can strike other nuclei and keep the chain
reaction going. Heavy water (deuterium oxide) is often used as a moderator. Fuel rods made of URANIUM
are separated by CONTROL rods (which control the chain reaction) made usually of cadmium or boron,
which absorb excess neutrons, and can prevent a reactor meltdown. The energy release by the fission
reaction is used to heat water to make steam to drive turbines to produce ELECTRICITY.
36. Nuclear reactors produce a lot of energy and are useful where there are no other sources of electricity. They
also don't pollute the air. However, they are expensive, only last about 35 years, produce toxic nuclear
WASTES that can be dangerous for hundreds of thousands of years, and can cause terrible damage if there
is an accident causes a reactor MELTDOWN like there was in 1986 at Chernobyl.
37. Nuclear fusion is a different type of reaction. In nuclear fusion, SMALL nuclei are fused together to form
LARGER nuclei. In the process, a great deal of energy can be made. This is the type of reaction that takes
place within the sun and stars, as well as within hydrogen bombs. A typical nuclear fusion reaction fuses
HYDROGEN atoms together.
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