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18. Atomic and Nuclear Physics eLearn.Punjab
However, alpha particles have the greatest power of ionization For Your Information
as compared to beta particles and gamma rays. It is due to
large positive charge and large mass of alpha particles. Beta i . Nuclear radiation is measured in unit of
roentgen equivalent man (rem), a unit of
particles ionize a gas much less than alpha particles do. The equivalent dose.
ionization power of gamma rays is even less than that of beta ii. Patient should be exposed to X-rays
with the limit of 0.1 to 1.0 rem.
particles. Ionization of three radiations in gas is shown in iii. Safe limit of radiation exposure is 5.0
Fig. 18.5. rem per year.
Fig. 18.5: Ionization effect of radiations in a gas
Penetrating Ability
The strength of radiations to penetrate a certain material is called penetrating power. The alpha
particle has the shortest range because of its strong interacting or ionizing power. The gamma
rays can penetrate a considerable thickness of concrete. It is due to their large speed and neutral
nature.
The beta radiation strongly
interacts with matter due
to its charge and has a
short range as compared
to gamma radiations. Fig.
18.6 shows the relative
penetrating abilities of
three kinds of radiations.
Fig.18.6: Penetrating power of radiations in different materials
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