Radioactivity Assignment complete with experiment

 

Radioactivity



Background:


Henri Becquerel was a french scientist who discovered radioactivity in 1896, it was an accidental discovery.

Henri at that time studied luminous material, luminous material is of two types one Fluorescent and the other is phosphor- descent .


Henri was so much inspired with the recent discovery of x-rays. After this discovery Henri found proof of radioactivity, while inves- tigating how uranium is influenced by light, He found that urani- um produce rays that can penetrate many material, and blacken the photographic plate even in the darkness.


For invesigate further there was another two scientist named as Pierre curie and his partner Marie curie, they both investigating many material to find science of radioactivity.


From uranium these both scientist able to sucessfully extract two others radioactive elements name as radium and the other one is polonium.


And after these discoviers , Henri Becquerel , Pierre and marrie were awarded the noble prize in physics in 1903.


Natural Radioactivity:


Radiation based activities are known as radioactivity, Radations means energy released in the form of wave .


Now the radiations which are naturally emitted are known as natural radioactivity,means no extenral conditions or energy is delivered , radiations emit even in the room temperature.


Elements in periodic table having a large atomic number are the elements which emit radiations naturally . Because these ele- ments are unstable. so,,,


The spontanous process of unstable nucleus emitting radioac- tive emission to become more stable is known as Radioactivity.


The reason why this process is called spontanous beacause the process is neither effected by chemical compostion also not ef- fected by any physical condition.


Radioactive elements:


Elements which shows radioactivity are known as radio- active elements.

Radioactive elements are

.Thorium,

.Radium,

.Uranium,

.Radon and

.Polonium.


Radioactivity experiment to study the nature of radia- tions:







In the above diagram a radioactive substance placed under the lead box, this radioactive substance emit radiations,These radia- tions emitted in the form of rays.


In this experiment we also placed two electrically charged plates one is positive charged plate and the other one is negative plate. The rays which are emitted through the substance are deflected in different directions as you see in the above figure.

The rays which are deflected towards the negatively charged plate are called Alpha rays.


And the rays which are deflected towards positively charged plate are called Beta rays.


The rays which travels straight without any deflection are called Gemma rays.

Alpha Particles:


Whenever a nucleus have too many protons, then it re- leases an aplha particle and as a result it try to reduce the num- ber of protons in the nucleus and its try to acheive a stable state.


In Alpha decay , when a radioactive nuclus disantegrate,the atomic number decreases by two and mass number decreases by four,the alpha decay is

zXᴬ →zYᴬ-₄ +₂He₄


Properties of Alpha radiation:


>Alpha particles has two neutrons and also has two protons.


>Alpha particles are the particles which are positively charged. (because it has two neutrons which are neutral and two protons which are positive so it has postive charge)


>They are helium nuclei..


>Alpha particles have low penetrating power ,and they are easi- ly stopped by any thin paper.


>The particles in which have high ionization power in the gas through which they have passed.


>They are easily deflected by magnetic and electric filed.


>Velocity of these particles is 1/10 th the velocity of light.

Beta Particles:


When ratio of neutrons to protons is high in a nucleus , then beta decay actually occurs here neutron transform into pro- ton and also an electron.


In beta decay, when radioactive nucleus is desantegrate by emit- ting a beta particle,,then Atomic number increases by one,and here the mass number remain same.The beta decay is,,,

zXᴬ → z+1Yᴬ + -1 eᵒ


Properties of beta radiations:


>These rays consist of negativity charged particles


>Velocity of beta rays is same as the velocity of light.


>The penetrating power of beta rays is very much greater ,they can easily pass through thick aluminium sheet.


>Due to high penetrating power its ionization is less.


>Each ray has charge of -1e


>These rays also effect the photographic plate


>The beta particles are deflected by magnetic and electric field also.


Gamma Particles:


After the emmision of either alpha or beta particle, in some cases the nucleus remains in their excited state,now in or- der to attain a low energy state the nucleus emit gamma rays.


In gamma decay,when a radioactive nucleus emit the gamma rays, the atomic number and the mass number remains same ,on- ly the energy level of the nucleus changes.

During alpha and beta decay, the daughter nucleus is in the ex- cited state, it only comes to ground state when gamma rays emit- ted.


Properties of gamma radiations:


>The gamma rays are actually X rays and it has very small wavelength.


>The penetrating power of gamma rays is very much greater even that of X rays.


>High penetrating power result as low ionization of gas


>It is not deflected by magnetic and electric field.


>They are only deflected by X rays


> They have no charge.

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