Page 178 - Physics 10_Float

ATOMIC AND NUCLEAR PHYSICS

1. Alpha ()-decay
General Equation:
A
4

X A-4 Y + He + Energy For your information
Z
2
Z-2
parent daughter -particle The SI unit for radioactivity is
the becquerel, Bq. In SI base
nuclide nuclide units, 1 Bq = 1disintegration
4

Example: 226 Ra 222 Rn + He + Energy
88 86 2 per second (dps). This is a very
radium radon -particle small unit. For example, 1.0 g
It means in alpha decay, the proton number or atomic of radium has an activity of
10
3.7 3 × 10 Bq. Therefore, the
number Z of the parent nuclide reduces by 2 and its mass
number or nucleon number A decreases by 4. kilobecquerel (kBq) and the
megabecquerel (MBq) are
commonly used. The activity
2. Beta ()-decay of 1.0 g of radium is
4
General Equation: 3.73×10 MBq.
A
0
A

Z Z+1 Y + e + Energy

Z
-1
parent daughter -particle
nuclide nuclide
14
0
14
Example: C N + e + Energy

-1
6
6
carbon nitrogen -particle

In beta ( )-decay , the parent nuclide has its proton number Z 
increased by 1 but its mass number or nucleon number A
remains unchanged.
3. Gamma ()-decay
General Equation:
A Z

Z X X + 
6
parent daughter gamma rays
nuclide nuclide
0
60

Example: 60 Co Co +  + Energy Physics Insight

27 27 0
cobalt cobalt -rays when alpha and beta particles
are slowed down by collisions,
Gamma rays are usually emitted alongwith either an alpha or
they become harmless. in fact,
a beta particle. they combine to form neutral
Nature and Properties of Radiations helium atoms.
Alpha particle is a helium nucleus comprising of two protons
and two neutrons with a charge of 2e. An unstable nucleus
with large protons and neutrons may decay by emitting alpha
radiations. . Beta radiation is a stream of high-energy
electrons. An unstable nuclei with excess of neutrons may
eject beta radiations. Gamma radiations are fast moving light
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