This document discusses the three main types of radioactive emissions: alpha particles, beta particles, and gamma radiation.
Alpha particles are made up of two protons and two neutrons and are the least penetrating emission. Beta particles can be emitted as electrons or positrons. Gamma radiation involves the emission of electromagnetic radiation from an excited nucleus as it transitions to the ground state.
The document explains the key properties and effects of each type of emission, and how they result in the radioactive decay and transmutation of elements in a decay series until a stable nuclide is reached.
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Alpha and Beta Particles and Gamma Radiation.pptx
1. Physics for senior secondary
or A-level students
~lalit kishore, The plenum School, HP
2. Genesis
There exist elements with unstable nuclei
Reason: The neutron-proton combination is such that
the forces between nucleons get unbalanced
To become stable they emit 2 things
Particles ...and/or
Electro-magnetic radiations
Such nuclei are called radioactive and the emission is
called radioactivity
3. Three types of emissions from
radioactive nuclei
Types of radioactive emission are:
Alpha-particles
Beta-particles
Gamma radiations
Notes:
All three emissions originate from nucleus of a
radioactive atom
Emissions are invisible to the eye
They are detected by impressions in the form of tracks
on high density photographic films or nuclear emulsion
plates
4. Alpha-particles -1
Composition
2 protons plus 2 neutrons
Properties
High speed ~ 10 raised
power minus 7 m/s Or 5%
speed of light
Least penetrating
emission (passes thro’
paper, not card, range in
air= few cm)
Interact with nearby
atoms to ionised
them...produce 10x5 ion
pairs per cm travel
5. Alpha particles - 2
An alpha particle is the
nucleus of helium atom
When an atom emits alpha-
particle, it is said to undergo
alpha-decay by loosing 2
protons and 2 neutrons
With alpha decay, one
element changes to another
and this process is called
transmutation
• Emitted alpha particles
have the same KE
6. Beta particles - 1
Some radioactive elements
such radioactive lead and
radioactive phosphorus
electrons and positrons
respectively as beta
particles along with
neutron particles
Even free neutrons and
protons undergo decay to
emit electron and positron
along with production of
energy
7. Beta particles - 2
In beta-minus decay in which negative electron is emitted,
a daughter nuclide is formed with:
Proton no. increased by 1
Nucleon no. remaining unchanged
In beta-plus decay in which positive electron (positron) is
emitted, a daughter nuclide is formed with:
Proton no. decreased by 1
Nucleon no. remaining unchanged
• Emitted beta particles have continuous range of KE
since the process is accompanied by emission of
neutrinos
8. Gamma radiations - 1
Some radioactive emit gamma
radiations which are
Part of e-m spectrum
Wavelength of the radiations is 10
raised power -11 to -13 metres
Can penetrate
Air to unlimited range
Several metres of concrete
Several cm of lead
Gamma emission, there is no
change in proton no. and
nucleon no. since no particles
are given out
They have weak ionising power
9. Gamma radiations – 2: Process
Energy emitted as gamma radiation to come to ground state
Change in ratio of protons to neutrons
Daughter nuclei still with excess energy Try to return to ground state
Radioactive element (thorium) emitting alpha and beta particles
Unstable nuclei Excess energy
10. Radioactive decay series
The nuclide may be unstable, further
decay happens to give different
nuclide
Sequence of decays till stable nuclide
is reached is called decay series
Do some reference work to find the
decay series uranium-238