X-rays, gamma rays and beta particles are all used in medicine to treat internal organs. X-rays are produced by firing electrons at a metal target and gamma rays are emitted by the nucleus of radioactive atoms. Gamma rays are used to kill cancer cells, to sterilize medical equipment and in radioactive tracers.

 1.Iodine - 131 it is use for functioning of Thyroid gland. It detect using radio active Iodine - 131

2.Radioactive phosphorus is known as P-32. It is a radioactive form of sodium phosphate. It is used as a treatment for some blood disorders.

3.Cobalt therapy or cobalt-60 therapy is the medical use of gamma rays from the radioisotope cobalt-60 to treat conditions such as cancer.

4.The sulfate ions in the solution contained radioactive sulfur atoms – ³⁵ S. The purpose of this investigation was to investigate active transport, that is, a process that uses energy to transport useful substances across cell membranes.

Here, the activity of the radioactive sample reduces to half in $140$ days. Therefore, the half life of the sample is $140$ days. $280$ days is it's two half lives. So before two half lives it's activity was

$\begin{array}{l} Hence, \ \frac { N }{ { { N _{ 0 } } } } =0.03=\left( { -\lambda t } \right)  \ In\left( { 0.03 } \right) =-\lambda t=\frac { { -In\left( 2 \right) \times t } }{ { \frac { { { T _{ 1 } } } }{ 2 }  } }  \ t=\frac { { In\left( { 0.03 } \right) \times \frac { { { T _{ 1 } } } }{ 2 }  } }{ { -In\left( 2 \right)  } } =63.24\, years \end{array}$

Tracers are a common application of radioisotopes. A tracer is a radioactive element whose pathway through which a chemical reaction can be followed. Tracers are commonly used in the medical field and in the study of plants and animals. Radioactive Iodine-131 can be used to study the function of the thyroid gland assisting in detecting disease.

According to Einstein if a body moves almost more than the velocity of light then it starts losing its mass.He gave this concept by a formula that is $E=m c^{2}$.Hence for the body to maintain constant mass it has to move with the speed less than the velocity of light.

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Iodine in food is absorbed by the body and preferentially concentrated in the thyroid where it is needed for the functioning of that gland. Thus the health problem related to thyroid can be diagnosed by Iodine−131 radioisotope. 

Gamma ray (also called gamma radiation) is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy.

Alpha particles have large kinetic energy and momentum with them. They are used to bombard the atomic nuclei to convert one element into another (for transmutation)

The isotopes of nearly all the elements of atomic number higher than 82 (i.e. lead) are radioactive. There are called the natural radioactive substances.

Substances which disintegrate (or decay) by the spontaneous emission of radiations are called the radioactive substances. Eq. Uranium, radium, polonium, thorium, actinium etc.

The atoms having radioactive properties are called radio isotopes. The nucleus of an atom becomes radioactive when the number of neutrons in the nucleus exceeds the number of protons inside it. $ _{6}C^{14},  _{27}Co^{60},  _{6}C^{12},  _{19}K^{40}$ etc are all examples of naturally occurring radio isotopes. However, they can also be prepared artificially by nuclear transmutation.

The age of fossils can be estimated by the study of decay of radioactive carbon atom $ _{6}C^{14}$ in the remains of the dead and decaying material. This process is called carbon dating.

Any physical changes (temperature, pressure and temperatures) or chemical changes do not alter the rate of decay of the radioactive substances.

Carbon−14 is used by an archaeologist to determine the age of an artifact, in percentage.
The ratio C-14 / C-12 in fresh sample is compared with the ratio in dead sample.