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• WHAT IS RADIATION ?
• TYPES OF RADIATION
• DISCOVERY OF X RAYS
• DISCOVERY OF RADIOACTIVITY
• RADIUM GIRLS
• NUCLEAR POWER PLANT
• CHERNOBYL ACCIDENT
• In general , Radiation is the emission and
propagation of energy in the form of waves or
• Eg :Sound ,light, x-rays , UV rays , Heat etc
• It can travel through medium or vacuum.
• In Physics, we take radiation in the form of
electromagnetic waves or particles.
• Eg :light, x-rays , UV rays etc
A TOUCH OF QUANTUM MECHANICS
• The idea of a radiation being a wave or particle
became vague when the WAVE PARTICLE theory
came into the scene .
• DE BROGLIE hypothesis says that the wave can act as
a particle sometimes and also sometimes electrons
,protons etc can behave as waves.
• This can be clearly explained by the PHOTOELECTRIC
• De Broglie wavelength is given by Lambda=h/p
Or h/mv .
• λ is indirectly proportional to velocity and
• All the macroscopic bodies do have
wavelength associated with them but that is
too small to observed.eg football
• Also Heisenberg uncertainty principle says
that when we try to find the position its
momentum become undefined and vice versa
PANJAB UNIVERSITY 6
MORE ABOUT HEISENBERG
• The uncertainty principle says that we cannot
measure the position (x) and the momentum (p)
of a particle with absolute precision.
• The more accurately we know one of these
values, the less accurately we know the other.
• Multiplying together the errors in the
measurements of these values has to give a
number greater than or equal to half of a
constant called "h-bar".
• This is equal to Planck's constant (usually written
as h) divided by 2π.
PANJAB UNIVERSITY 7
• One way to think about the uncertainty principle is as an
extension of how we see and measure things in the everyday
• You can read these words because particles of light, photons,
have bounced off the screen or paper and reached your eyes.
Each photon on that path carries with it some information
about the surface it has bounced from, at the speed of light.
• Seeing a electron, is not so simple. You might similarly
bounce a photon off it and then hope to detect that photon
with an instrument.
• But chances are that the photon will impart some momentum
to the electron as it hits it and change the path of the particle
you are trying to measure. Or else, given that quantum
particles often move so fast, the electron may no longer be in
the place it was when the photon originally bounced off it.
PANJAB UNIVERSITY 8
– Higher energy electromagnetic waves (gamma) or
heavy particles (beta and alpha).
– High enough energy to pull electron from orbit.
– Lower energy electromagnetic waves.
– Not enough energy to pull electron from orbit, but
can excite the electron.
TYPES OF IONISING RADIATION
1.DIRECTLY IONISING RADIATION
• Energy > 13.6 ev
• Ionisation of an atom
• Eg : electrons , protons or alpha ,beta etc
2. INDIRECTLY IONISING RADIATION
• Energy <13.6 ev
• Two step interaction
• Eg x rays , gamma rays etc
Can a non ionising radiation be
an indirectly ionising one ?
FOOD FOR THOUGHT ...
• Wilhelm Conrad Roentgen , a German physicist
discovered X rays on November 8,1895.
• He was investigating the behaviour of cathode rays in
high energy cathode ray tube
• It consists of a glass envelope from as much air as
possible was evacuated
• He covered the CRT with black paper to ensure that
light does not escape and also to block outside light .
• He also darkened the laboratory room .
• He found that whenever the cathode ray was
organised the unknown type of ray was
• This ray caused the fluorescence of a small
paper coated with barium platinocyanide .
• This could not be electrons from cathode ray
• This could not be the light because it is all dark
and cardboard was also there in between them.
• There is something that cross the tube when CRT
is organised and also penetrate the cardboard
• Excitement increased and he kept different things
in between them replacing cardboard results
• Then he held his hand between the tube and the
fluorescent screen and the result was ...
• HENRI BECQUEREL was a scientist who worked on
minerals and optics .
• He belonged to a family of scientist ,Grandfather
discovered piezoelectricity and father phosphoresce.
• After discovery of x rays , Becquerel was trying to find
out whether these are related to phosphorescence or
• He took Uranium salts and photographic film covered
with black paper and thought if the X-rays were coming
out from phosphorescent* material it will cross film
and form a image provided we need to give a UV
radiations ie Sun.
• Those days in February , Paris was short of sunshine .
• Becquerel had to delay his experiment .He kept the
Uranium minerals and film in the drawer .
• After week or so he decided to develop film though
sunshine was not there
• He found that the photographic film had an impression
• Even when uranium was not phosphorescent .
• He was dumbstruck ,seeing it as he hypothesised that
Uranium salts are sources of X-rays .
• To continue the research RUTHERFORD came
• His topic of concern was to study the rays given out
• He discovered that the rays by Uranium are not X
rays they are some other rays .
• He gave three rays alpha beta and gamma which
comes from some special substance
AND IT DIDNOT STOP!
MARIE CURIE : MOTHER OF MODERN PHYSICS
• The term radioactivity was actually coined by Marie Curie,
who together with her husband Pierre, began investigating
the phenomenon recently discovered by Becquerel.
• She worked on the uranium ore pitchblende and found that
it emitted much more radioactivity than the uranium in the
mineral could deliver .
• It must contain another highly radioactive element, yet
• In 1898, PIERRE AND MARIE ,discovered two new elements
- polonium and radium.
• Polonium was named after Marie's homeland, Poland.
Radium got its name from the Latin word for ray..
• There was a factory of radium watches which
hired 70 WOMEN to paint RADIUM DIAL .
• Ii was called UNDARK paint made of glue ,water
and radium powder .
• Women wee taught to shape paintbrush with
mouths to maintain a fine point
• Some painted their nails and teeth too with that
• Management and scientist kept themselves away
from the exposure but the workers were unaware
of it .
• Five Radium Girls sued U.S.
Radium in a case that
initiated labour safety
standards and workers'
• Workers suffered from
inexplicable bone fractures,
bleeding gums and
eventually, necrosis of the
• The Radium Girls' case was
settled in 1928, putting a
swift end to shaping
paintbrushes with the
mouth and open containers
of radium paint.
NUCLEAR POWER PLANT
• In nuclear power station, electrical power is
generated by nuclear reaction.
• Here, heavy radioactive elements such as Uranium
(U235) or Thorium (Th232) are subjected to nuclear
fission. This fission is done in a special apparatus
called as reactor.
• FISSION : The nuclei of heavy radioactive atoms are
broken into two nearly equal parts. During this
breaking ,huge quantity of energy is released. This
release of energy is due to mass defect. (mass of final
products are reduced than initial )
• It is same as steam power station. Only difference is
that, instead of using heat generated due to coal
combustion , here heat is generated due to fission
• Heat is used to produce steam from water in the
boiler. This steam is used to drive a steam turbine.
This turbine is the prime mover of the alternator
which generates electrical energy.
• Very less amount of nuclear fuel can generate huge
amount of electrical energy. This is the unique
feature of a nuclear power plant.
PANJAB UNIVERSITY 27
• One kg of uranium is equivalent to 4500
metric tons of high grade coal. That means
complete fission of 1 kg uranium can produce
as much heat as can be produced by complete
combustion of 4500 metric tons high grade
• To meet up conventional fuel crisis in present
era, nuclear power station can be the most
PANJAB UNIVERSITY 28
DIFFERENT COMPONENTS OF
NUCLEAR POWER STATION
The plant consists of mainly following parts:
1 NUCLEAR REACTOR
2 HEAT EXCHANGER
3 STEAM TURBINE
PANJAB UNIVERSITY 29
• In nuclear fission, the nuclei of nuclear fuel, such as U235
are bombarded by slow flow of neutrons.
• Uranium is broken, huge heat energy released and also
number of neutrons are emitted during breaking .
• These neutrons cause further fission which needs to be
• These neutrons should be removed otherwise explosion
can occur .
• Cadmium rods are used because they are good absorber
of neutrons called control rods they are moveable .
• There is also moderator to slow down the neutrons .
PANJAB UNIVERSITY 30
• Heat Exchanger: The heat carried by sodium metal,
is dissipated in water and water is converted to high
pressure steam here.
After releasing heat in water the sodium metal
coolant comes back to the reactor by means of
coolant circulating pump.
• Steam Turbine :In nuclear power plant, the steam
drives the turbine in the same way. After doing its
job, the exhaust steam comes into steam condenser
where it is condensed to water and can be reused.
• Alternator :an electrical generator that converts
mechanical energy to electrical energy in the form of
PANJAB UNIVERSITY 31
The worst manmade disaster in human history
Czech Technical University In Prague
23 May 2007
23 May 2007 Czech Technical University in Prague 34
WHERE IS CHERNOBYL?
• NUCLEAR power plant is located 11 miles from the city
• Plant consisted of 4 reactors while 5 and 6 reactors
were under construction each capable of producing
1GW of ELECTRIC POWER
• On Saturday, April 26, 1986, at 1:23:58 a.m. local time,
the fourth reactor of the Chernobyl power plant
known as Chernobyl-4 suffered a catastrophic steam
explosion that resulted in a fire, a series of additional
explosions, and a nuclear meltdown.
• It is regarded as the worst nuclear accident . It
produced radioactive debris that drifted over parts the
western soviet union Scandinavia, UK, and even
PANJAB UNIVERSITY 35
•Reactor 4 was undergoing a
test to test the backup power
supply in case of a power
•The power fell too low,
allowing the concentration of
xenon-135 to rise.
•The workers continued the
test, and in order to control
the rising levels of xenon-135,
the control rods were pulled
• The experiment involved shutting down the coolant
pumps, which caused the coolant to rapidly heat up and
• Pockets of steam formed in the coolant lines. When the
coolant expanded in this particular design, the power
level went up.
• All control rods were ordered to be inserted. As the rods
were inserted, they became deformed and stuck. The
reaction could not be stopped.
• The rods melted and the steam pressure caused an
explosion, which blew a hole in the roof
23 May 2007 Czech Technical University in Prague 39
• 5.5 million people still live in contaminated
• 31 people died in 3 months of radiation
• 134 emergency workers suffered from acute
• 25,000 rescue workers died since then of
diseases caused by radiation
• Increased birth defects, miscarriages, and
23 May 2007 Czech Technical University in Prague 40
• By the year 2000 there
were 1800 case of
thyroid cancer in
• High number of suicide
and violent death
policemen, and other
• Radiation detection and measurement by
• Christensen book on XRAY PRODUCTION
PANJAB UNIVERSITY 41
23 May 2007 Czech Technical University in Prague 42