98
II.
There are several definitions in the text. What are they? Complete the
sentences.
1.
Sometimes the nucleus of an atom is not stable. The change is called a
.
2.
Emitting particles or waves from the nucleus is called
.
3.
The
of a radioactive isotope
is the time after which, on
average, half of the original material will have decayed.
4.
is a random process which gives out heat.
5.
The particles or waves that
are emitted are called
.
III.
Are these sentences true or false?
1.
There are not natural radioactive materials in the ground at all.
2.
Uranium and plutonium are strongly radioactive but have very short
half-lives.
3.
The radiation was classified by E.
Rutherford as alpha, beta, and
gamma rays (for the first three letters of the Greek alphabet)
according to their ability to penetrate matter and ionize air.
4.
Radiation causes health problems by killing cells in the body, and the
amount and type of damage done depends
on the dose of radiation
received and the time over which the dose is spread out.
5.
Gamma radiation is the least penetrating of the three and will not
travel through several centimeters of lead.
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