ATOMIC AND
NUSLEAR PHYSICS
|
(table of contents). ·
Introduction. ·
Atom and atomic
nucleus. ·
Isotopes. ·
Natural
radioactivity. ·
Background
rediations |
introduction
SCIENTISTS were always interested to know about the smallest
particle of matter. Greek philosopher democrats in 585 BC postulated that
matter is build from small particles called atoms. The atoms mean indivisible
in greek language.
Ratherford in 1911, discovered that atom had a central part
called the nucleus of atom. In this unit, we will describe different aspects of
atomic and nuclear physics such as redioactivity, half-life, nuclear reactions,
fission and fussion.
ATOM AND
ATOMIC NUCLEUS.
Rutherford discovered that the postive charge in an atom was
concentrated in small regions called nucleus. The nucleus contains protons and
neutrons which are collectively called nucleans. Atom also contains electrons
which are revolving around in nerarly circular orbits about the postively
charged nucleus. The simplest atom is that of hydrogen, nucleus of which is a
single proton. We describe an element with respect to its nucleus and uses of
following quantities.
The atomic number is equal to the number of protons in the
nucleus.
The neutron number is equal to the number of neutrons in the
nucleus of atom.
The atomic mass number is equal to the number of protons and
neutrons in the nucleus of atom. The mass of neutron is nearly equal to that of
proton. But proton is about 1836 times havier than an electron.so the mass of
an atom isnearly equal to the sum of masses of proton and neutrons.
Generally, an atom is represented by the symbol x.
ISOTOPES.
Isotopes are atom of same elements having same atomic number
but different mass number. This because of difference of netrons in their
nuclei. There are three isotopes of hydrogen atom.
NATURAL
RADIOACTIVITY.
IN 1896,BACQUERAL accidently discovered that uranium salt
crystals emit an invisible rediation that can darken a photographic plates, he
also observed that the rediation had the ability to iinoised in gas. Subsequent
experiments by other scintists showed that other substances also emmited
rediations.
The most segnificant investigations of this type were
conducted by marie curie and her husband pierre. They discovered two new
alaments which emmits rediations. They were named polonium and radium. The
process of emition of rediations by some elements was called natural
redioactivity.
Subsequent experiments performed by hanri becqueral suggested
that radioactivity was resukt of the decay or disintegration of unstable
nuclei.
The spontaneous emission of rediation by unstable nuclai is
callede natural radioactivity. And the elements which emmits such rediations
are called as radioactive elements.
Three types of rediations are usually emmited by radioactive
ubstance. They are:alpha particle; beta particle and gamma rays. These three
forms of rediations were studied by using the scheme existed.
The radioactive source is placed inside the megnetic field
while beta ray does not change its direction. Three types of rediations can be
distinguished from their path followed in an external magnetic field.
BACKGROUND
REDIATIONS
REDIATIONS PRESENT IN ATMOSPHERE DUE TO DIFFERENT REDIOACTIVE
SUBSTANCES ARE CALLED BACKGROUND REDIATION.every where in rock, soil, water,
and air of our planet are traces with redioactive elements. This natural
rediation is called background rediation. It is a part of our environment as
sun shine and rain. Fortunatly, our bodies can tolerate it. Only places where
rediation is very high can be injurious to the health of living organisms.
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