RADIOACTIVITY, PROPERTIES OF RADIOACTIVE RAYS

RADIOACTIVITY
All the elements having atomic number greater than 82 emit invisible radiation all the time. The phenomenon of emission of these powerful rays is called "Natural Radioactivity" and the element that emits such rays is called "Radio Active Element".
TYPES OF RADIO ACTIVE RAYS
There are three types of radioactive rays: ·         α-Rays  ·         β-Rays ·         γ-Rays
·         PROPERTIES OF α-RAYS: -
(a) NATURE: α ray consists of α particle. Each α particle consists of Helium (2He4) nucleus.
(b) CHARGE: α particle carry positive charge.
(c) MASS: Mass of each α - particle is 4 times that of a proton or H-atom.
(d) IONIZATION: Ionization power of α ray is very high.
(e) PENETRATION POWER: Penetration power of α ray is very small.
(f) FLUORESCENCE: α ray’s produce fluorescence in different substances.
(g) EFFECT ON HUMAN BODY: α ray produce burn and sore on human body.
(h) ARTIFICIAL RADIO ACTIVITY: α rays can produce artificial radioactivity is certain nuclei.
·         PROPERTIES OF β –RAYS: -
(a) NATURE: β rays consist of fast moving electrons.
(b) CHARGE: β rays have negative charge.
(c) VELOCITY: Velocity of β rays is from 9 x 107 m/sec to 27 x 107 m/sec.
(d) EFFECT ON PHOTO GRAPHIC PLATE:  β rays affect photo graphic plate
(e) IONIZATION POWER: Ionization power of β rays is very small.
(f) KINETIC ENERGY: Kinetic energy of β rays is less than that of β - rays.
(g) FLUORESCENCE: β rays produce fluorescence in different substance.
·         PROPERTIES OF γ – RAYS: -
(a) NATURE: γ rays are electromagnetic radiation.
(b) CHARGE: γ - rays are no charge.
(c) VELOCITY: γ - rays travel with the velocity of light that is 3 x 108 m/sec.
(d) PENETRATION POWER: Penetration power of γ - rays is very large. It is about hundred times larger than that of γ rays.
(e) FLUORESCENCE: γ - rays produce feeble fluorescence When incident on screen coated with barium platino cyanide.