(i) Radioactive materials should be kept in thick walled lead container.
(ii) Lead coated aprons and lead gloves should be used while working with hazardous radioactive materials.
(iii) We should avoid eating while handling radioactive materials.
(iv) The radioactive materials should be handled only by tongs or by a remote control process.
(v) Dosimeters should be worn by the users to check the level of radiation.

Medical applications of radioisotopes can be divided into two parts
i) Diagnosis ii) Therapy Radio. 
Isotopes are used as tracers to diagnose the nature of blood circulatory disorders, defects of bone metabolism, to locate tumors, etc. Some of the radio isotopes which are used as tracers are: hydrogen, carbon, nitrogen, sulfur, etc.
(i) Radio sodium (Na²⁴) is used for the effective functioning of heart.
(ii) Radio - Iodine (I¹³¹) is used to cure the goiter.
(iii) Radio iron is (Fe⁵⁹) is used to diagnose anemia and also provide treatment for the same.
(iv) Radio phosphorous (P³²) is used in the treatment of skin diseases.
(v) Radio cobalt (Co⁶⁰) and radio gold (Au⁷⁹) are used in the treatment of skin cancer.
(vi) Radiations are used to sterilize the surgical devices as they can kill the germs and microbes.

(i) Atom bomb is based on the principle of uncontrolled chain reaction.
(ii) In an uncontrolled chain reaction, the number of neutrons and the number of fission reactions multiply almost in a geometrical progression.
(iii) This releases a huge amount of energy in a very small time interval and leads to explosion.
Structure:
(i) An atom bomb consists of a piece of fissile material whose mass is sub critical.
(ii) This piece has a cylindrical void. It has a cylindrical fissile material which can fit into this void and its mass is also sub critical.
(iii) When the bomb has to be exploded, this cylinder is injected into the void using a conventional explosive.
(iv) Now, the two pieces of fissile material add up to form super critical mass which leads to an explosion.
(v) During this explosion tremendous amount of energy in the form of heat, light and radiation is released.
(vi) A very high temperature and pressure are experienced in fraction of second along with hazardous radiation like ૪ rays which adversely affect the living creatures.

Soddy and Fagan's displacement laws:
(i) When a parent element emits an alpha particle the new element is formed with a decrease in atomic number by two and mass number by four.
(ii) When a parent nucleus emits a beta particle the daughter nucleus is formed with an increase in atomic number by one and has same mass number of the parent nucleus.
(iii) In gamma decay, the energy level of nucleus only changes. No new elements are formed.

(a) Controlled chain reaction:
(i) In the controlled chain reaction the number of neutrons released is maintained to be one.
(ii) This is achieved by absorbing the extra neutrons with a neutron absorber leaving only one neutron to produce further fission.
(iii) Thus, the reaction is sustained in a controlled manner.
(iv) The energy released due to controlled chain reaction can be utilized for constructive purpose.
(v) Controlled chain reaction is used in a nuclear reactor to produce energy in a sustained and controlled manner.
(b) Uncontrolled chain reaction:
(i) In the uncontrolled chain reaction the number of neutrons multiplies indefinitely and cause fission in a large amount of fissile material.
(ii) This results in the release of huge amount of energy within a fraction of second.
(iii) This kind of chain reaction is used in atom bomb to produce explosion.

(i) Cell phone companies are used non-ionised radiations.
(ii) It is not harmful like X-ray or gamma radiation.
(iii) In 2006 report issued by the WHO, human body absorbs energy from cell phone towers which is almost five times more than FM and Television.
(iv) Signals from each mobile towers travels a few miles from there.
(v) The closer we are the greater the danger.

(i) The intensity of radiation used in X-ray machine is small, so the chance that X-ray will cause severe problems is very low.
(ii) X-ray posses almost equal energy like gamma radiation.
(iii) So, if we take often, it may destructive living cell present in our body.
(iv) It may leads to cancer.

In alpha decay atomic number decreases by two and mass number decreases by four. So
232 - 208 = 24
Mass number decreased by 24. So 6 alpha particle would come out.
\({ }_{90} \mathrm{X}^{232} \rightarrow{ }_{78} \mathrm{Y}^{208}+6{ }_{2} \mathrm{He}^{4}\)
In beta decay atomic number increases by one
78 + 4 = 82
So, 4 beta particle would come out.
\({ }_{78} \mathrm{Y}^{208} \rightarrow{ }_{82} \mathrm{Z}^{208}+4_{-1} \mathrm{e}^{\mathrm{o}}\)
So, six alpha particle and four beta particles would come out.