Gamma-ray waves

Gamma rays are electromagnetic waves with the smallest wavelength (highest energy). The origin of this ray occurs from the smallest atom to the giant celestial body. In the radioactivity chapter, we have learned that it emits gamma rays when an atom shows radioactivity.

Besides radioactive decay, it also originated from very hot stars, black holes in the universe, and lightning. This wave, unlike alpha and beta, has no mass or charge. The penetration effect of this ray is also very high.

Discovery of gamma-ray wave

Gamma-ray was first observed during radioactive decay. In 1899, Ernest Rutherford first differentiated between this ray and the other two. Initially, he considered these rays as fast beta particles. But with the help of a magnetic field test, that old idea was rejected when it was established that it has no charged particle. In 1914, with the help of a reflection test on the crystal surface, it was proved that these rays were nothing but EM waves. 

Origin of gamma rays wave

As mentioned above, this ray is produced in different reactions, but we shall focus only on the radioactive decay reactions. 

During a radioactive decay reaction, alpha or beta occurs in a nucleus of an atom that gets excited. Just like an electron returns to its lower energy state by emitting photons (not a gamma-ray photon), in the same way, an excited “daughter” nucleus also emits photons of the lowest wavelengths for gaining stability. Such reactions are one of the important sources of gamma rays. Examples of such reactions are-

234Pa91(excited) —> 234Pa91 + γ

 (pa: protactinium)

 60Co27 —> 60Ni28* + e– + v–e + E

 60Ni28* —>  60Ni28 + γ 

There is another type of reaction where gamma rays are produced, called electron capture. This is the opposite process of beta production. An example of one such reaction is :

201Hg80 + -1e —> 201Au79 + γ 

Some other sources of gamma rays:

Gamma-ray bursts: This is the most powerful gamma explosion in the universe. It released more energy than the Sun can in its entire lifetime. 

Supernova: Massive amounts of gamma rays are produced during a supernova explosion. 

Lightning also produces gamma-rays in the Earth’s atmosphere. 

Properties of gamma rays

Before understanding the properties, we will first discuss some basic terms which are often used to describe the properties of waves. 

Ionising power / Ionisation potential

Ionising power of radiation is the capacity of that radiation to ionise other molecules when it is passed through it. Ionisation happens because when radiation passes through a medium, the atoms of that medium lose electrons and get ionised. The more this property, the more the radiation will have ionising power. For gamma rays, their ionising power is very low.

Penetration effect

There is another property called the penetration effect. Radiation can penetrate the human body walls and go through them. This is the penetration effect. More than capacity will be more penetrating will be that ray. Gamma rays have a high penetrating power. 

The more mass present, the more significant the ionising power and the lower the penetration power.

For a better understanding of the properties of gamma rays, let’s have a closer look at the different types of rays –

Three main rays originate due to radioactive decay. 

Alpha rays

These are nothing but streams of helium ions, basically produced inside the nucleus due to the breakdown of neutrons. So it contains a total of two neutrons and two protons. This is a very high energy wave having a positive charge and high ionisation potential. 

n → p+ + e- + ve

Beta rays

Beta rays are fast electrons produced inside the nucleus, as mentioned in the above reaction. It carries a negative charge and has a moderate amount of ionising power.

Gamma rays

As mentioned above, gamma rays are EM waves having a very high frequency. We have previously learned how an electron jumps from a higher energy orbit to a lower energy one by emitting photon particles in the form of X-rays. Analogically this phenomenon can also be considered the same. Here, the unstable “daughter” nucleus, formed by alpha or beta or both reactions, gets stability by emitting high-frequency photons in gamma-rays. 

Usages of gamma rays :

1. One of the most important uses of gamma rays is cancer treatment. Using radiotherapy, cancer cells are killed and done by gamma rays. 
2. Gamma rays often do the sterilisation process of medical equipment. 
3. To check weak points in a large oil pipeline.
4. They are used in nuclear reactors. 
5. Scientists use them to detect astronomical objects. 

Harmful effects of gamma rays :

1. Mild radiation sickness: Because of the minimal dose of gamma for a prolonged time.Fatigue weakness can occur.

1. Severe radiation sickness: problems like skin burn, hair loss, headache, poor healing can occur.
2. Cancer: Being exposed to gamma rays for a long time can cause cancer (blood, hepatic etc.). 

Conclusion

So in the above discussion, we learnt the origin, properties, usage and harmful effects of gamma rays. Gamma rays are one of the essential types of EM waves. Due to its very high value of penetration power, an object that radiates these rays are conserved in lead-coated boxes. In physics and astronomy, these rays have immense uses. For example, with the help of gamma-ray spectroscopy, scientists measure the amount of gamma-ray radiated from a sample and by measuring this amount, different elements can be identified. Researchers apply this concept to know the geochemistry composition of other planets.