A beta particle (β-particle) is an electron or positron having very high speed and energy and is emitted during radioactive decay of nucleus during beta decay process. Beta particles with energy of 0.5 MeV have a range of about one meter in air. They are a type of ionizing radiations and beta particles charge is negative as they are defined as fast moving electrons. In simple words, beta rays can be defined as a beam of electrons or positrons. So they possess negative charge unlike x rays and gamma rays which are charge less. Since beta particles are produced in beta decay process so firstly we will understand that what are beta particles and beta decay.
What is beta decay?
Beta decay occurs when there are too many protons or neutrons, then one of proton or neutron is transformed into other one according to situation. Beta decay is of 2 types, positive beta decay and negative beta decay.
In β− decay, a neutron decays into proton, electron and anti-neutrino and in this way one neutron is reduced and one proton is increased inside nucleus. In this process electrons are produced as products.
n → p + e– + ve –
In β+ decay, a proton decays into neutron, positron and neutrino and in this way one proton is reduced from total and one neutron is increased. In this process positrons are produced as products.
p → n + e+ + ve
Both of these decay processes happen instantaneously and they are not triggered by any source, it happens in an atom when number of p and n exceeds. When neutron and proton exchanges then atom is also changed to other as its atomic number gets changed.
Interaction with matter
Out of alpha, beta and gamma rays, beta rays have medium ionizing power. When they decelerate in matter, they produce secondary gamma rays which are more penetrating. Since they are composed of charged particles, their ionizing power is much more than gamma rays. When beta rays pass through matter, they can be decelerated by interaction with matter, which can lead to the production of bremsstrahlung x rays.
How are beta particles formed?
They are found in natural radioisotopes found in radioactive decay.
- Lead-210, Bismuth-214, Thallium-206
- Also found in radioactive products of nuclear fission like Strontium-90, Caesium-137, Tritium
Comparison of alpha, beta and gamma rays
Alpha particles are most ionizing and gamma rays are least ionizing. Conversely, penetration power of alpha particles is less and of gamma rays is more since alpha particles are massive. Out of a human body, gamma rays are more dangerous than alpha as they can penetrate. Alpha particles are helium nuclei and they have positive charge while beta particles are fast moving electrons and own negative charge. Gamma rays are charge less. One interesting thing to notice is that alpha and beta are particles but gamma rays are in form of radiations and since these rays lie in electromagnetic spectrum so they travel with speed of light. In this respect, speed of gamma rays is greater than that of alpha or beta particles. Similarly, from above 3, alpha particles are more massive, while beta particles have less mass and gamma rays have zero mass.
Properties of beta particles
- The mass of beta particles is half of one thousands of mass of proton
- They have positive or negative charge.
- Since thy have less mass so they move quickly through matter around at speed of light.
- They lose energy quickly as they interact with matter.
- The ionizing power of beta particles is less than that of alpha particles so they are less hazardous.
- They can travel greater distance in air as their mass is less.
- If beta particles are inhaled or ingested then they can damage internal organs and cells.
- They have high speed and energy.
- They have negative or positive charge and are produced by beta decay process.
- They get deflected by electric and magnetic fields as they are charged.
- They can produce phosphorescence (Radiation emission similar to fluorescence except on a longer time span, so emissions persist until excitation has stopped).
- They can affect photographic plate.
Are bananas radioactive?
Yes bananas are radioactive. If you are able to eat 10,000,000 bananas at once, then you die by radiation poisoning.
A potassium isotope is the element which makes bananas officially radioactive food. Potassium-40 (K-40) contains around.01 percent of all potassium. It has a half-life of about 1.25 billion years, ensuring it will not go anywhere. K-40 degrades two distinct forms. One of the neutrons decays to a proton approximately 89 percent of the time, turning it from potassium to calcium. When it does so, it emits an electron-a beta particle. Potassium decays about 11 per cent of the time by trapping an electron and converting one of the protons into a neutron. When it does so it emits gamma rays-radiation with very high intensity. Exposure to sufficient beta-radiation or gamma radiation can cause radiation sickness and high cancer rates.
Other foods that are radioactive include potatoes, nuts (especially Brazil nuts), and kidney beans. So, a potato and kidney bean stew with banana nut bread for dessert will be the ideal radioactive dinner.
Uses of beta radiation
- Beta particle sources like strontium-89 are used to treat eyes and bone cancer.
- They are used to find out the thickness for quality control of some material like paper. It is done by estimating the amount of absorbed radiation.
- Positive beta decay is a source of positrons which are used in positron emission topography (PET scan).
- They ca penetrate in living tissues so can cause mutation in DNA.
- Beta sources are used to kill cancerous cells in radiation therapy.
- Tritium is used in phosphorescent lightening, requiring no power.
- Fluorine-18 is used in PET.
- Radioisotopes are commonly used as tracers in chemical and biological research.