Category: Physics Notes PPT

The concept of phonon was introduced by soviet physicist Igor Tamm in 1932. The word phonon was derived from the Greek word phone, which refers to the meaning of sound or voice because long-wavelength phonons result in the production of sound. The name and the word are analogous to the photon. In analogy with the quantum energy, photon, in the electromagnetic field, the name phonon was suggested for the quantum lattice vibrational energy by Frenkel in 1935. Thus, phonons are the quanta of sound just like a photon is a quanta or the packet of energy for electromagnetic waves.

In this article, we are going to learn about the concept of phonons, what phonons are and a deep insight into the meaning of phonons for better understanding.

What is Phonon?

• Solid crystal consists of atoms bound into a specific repeating three-dimensional spatial pattern called a lattice.

• The solids execute elastic behaviour at the atomic level, the bond between the atoms and the intermolecular bonds are elastic.

• The atoms act like they are connected with a spring, just like coupled harmonic oscillators and the thermal energy generated or any external forces will cause the atoms and molecules to oscillate. This will generate mechanical waves that carry heat and sound through the material.

• A packet of these waves can travel throughout the crystal with definite momentum and energy known as phonons.

• Now, what is phonon? The quantum of energy is a phonon. In other words, we can say, a phonon is the quantum energy of the lattice vibration, just like photons are the quantum energy of electromagnetic radiations. The energy of each phonon is given by:

⇒ E = hv

⇒E = ħ(2π)v

⇒ E = ħω……. (1)

Where,

ω -The angular frequency

ħ – The reduced Planck’s constant

Phonon Meaning

• According to the phonon definition, a phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules condensed specifically in solids and some liquids. In other words, a phonon can be defined as a discrete unit of vibrational mechanical energy, the phonons exist with a discrete amount of energy given by E=ħ.

• Phonons play an important role in many of the physical properties of solid states, such as they play a key role in thermal conductivity and electrical conductivity. The study of phonons is an essential concept in condensed matter physics or solid-state physics.

• Phonon Vector: When a phonon with a wave vector is created by elastic scattering of a photon or neutron from wave vector K to K’, the wave vector selection rule that governs the process is given by:

⇒ K = K’ + G

Where,

G -The reciprocal lattice vector

Types of Phonon

When the unit cell consists of more than one atom, the crystal will contain two types of phonons. Thus, there are two types of phonons that we study in condensed matter physics:

Phonon Energy

Since, the atoms in the unit cell are behaving like a coupled oscillator, according to the quantum theory, the energy of the harmonic oscillator is given by

[Rightarrow E = (1+frac{1}{2}bar{h}omega)]       

Where,

ω -The angular frequency

ħ – The reduced Planck’s constant

Phonon Momentum

The phonon momentum is given by ħK, it is not the momentum of the phonon, it is often referred to as crystal momentum in general.

Properties of Phonons

• Phonons are often used as a quasiparticle, some popular research has shown that phonons and protons may indeed have some kind of mass and be affected by gravity.

• phonons are said to have a kind of negative mass and negative gravity.

• phonons are known to travel faster (with maximum velocity) in denser materials.

• It is projected that phonons would deflect away as it detects the difference in densities, exhibiting the qualities of a negative gravitational field.

• Phonons have also been predicted to play a key role.

• They can also be used as quasiparticles.

• They can be affected by gravity.

• They tend to have negative energy and negative mass.

• They travel faster in denser material (with higher velocity).

Phonons in Semiconductors

The lattice thermal conductivity of a number of semiconductors along with InSb, GaAs, GaSb, CdTe, and CdS has been measured between temperatures 1.7 and 300°K. This, together with previous works and experiments on Si and Ge, is used to investigate the validity of the relaxation time expressions for the scattering of phonons by boundaries, atomic impurities and electrons, and to discuss phonon-phonon interactions and resonance scattering effects. 

The obtained results indicate that the boundary scattering and isotope scattering relaxation times lead to accurately calculated values of thermal conductivity only when the materials are exceptionally pure. And the structure, which has been identified as due to resonance scattering, has been observed in the data for most of the materials. Electron-phonon scattering has been noted in GaSb but the complexity of the problems make the analysis only qualitative. The phonon-phonon scattering is further studied into two more processes known as the U-process and N-process.

The limit scattering and isotope scattering unwinding times lead to precisely determined upsides of warm conductivity just when the materials are uncommonly unadulterated. Also, the construction, which has been distinguished because of reverberation scattering, has been seen in the information for the majority of the materials. Electron-phonon scattering has been noted in GaSb however the intricacy of the issues makes the examination just subjective. The phonon-phonon scattering was additionally examined into two additional cycles known as the U-interaction and N-process.

Did You Know?

Phonons are analogous to photons, in fact, both possess almost identical properties. The following points will elaborate on why phonons are analogous to photons:

• Both phonons and photons are bosons. That means, both particles with integral spins.

• Both photons and phonons are the quanta of energy. Photons are the quanta of energy described for electromagnetic waves, whereas phonons are the quanta of energy for the lattice vibrations.

• Photons and phonons are not conserved entities.

Planetary nebula refers to any class of bright nebulae that are expanding shells composed of luminous gases. The origin of these glowing gases is flying stars in the universe. When you observe planetary nebulae through a telescope, you will see that they have a relatively compact appearance that is different from the regular formation of nebulae. Usually, a nebula has chaotic patchy shapes of other nebulae. Planetary nebulae are called so because they resemble planetary disks. The first planetary nebulae were discovered in the 1700s. 

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Planetary Nebula Definition 

Planetary Nebula is a small object having a radius of 1 light-year and a mass of gas of around 0.3 solid mass. These are the remains of stars that once looked like the sun. Planetary nebulas spend their lives in the universe turning hydrogen into helium. These massive fusion reactions happen in the core of the planetary nebula. 

When the hydrogen runs out during the fusion reaction, the star uses helium as a replacement fuel source. However, the helium source burns heavier than a combination of carbon, nitrogen, and oxygen. Eventually, the helium source is exhausted, and the star dies. When the star dies, it puffs off its outer gaseous layer and leaves behind a tiny, hot, dense core called the white dwarf. It is the size of planet earth but has a mass that is close to an original star. 

The glow from planetary nebulae is intriguing as it spreads across the broad swath of the spectrum. It goes from ultraviolet to infrared. Some examples of the planetary nebula are Helix nebula, butterfly nebula, engraved hourglass nebula, Saturn nebula, dumbbell nebula, and stingray nebula. 

Forms and Structures of Planetary Nebulae

There are around three thousand planetary nebulae in our galaxy. Most of these nebulae are found suitable in the centre of our galaxy, the Milky Way. Here are some of the planetary nebulae seen in our universe: 

Helix Nebula

Among these three thousand is the Helix Nebula, which is one of the largest-known planetary nebulae. The Helix Nebula is also referred to as the NGC 7293 and is found in the Aquarius constellation. It subtends at an angle of about twenty minutes of arc and is the two-thirds angular size of the Moon. 

It was discovered in the 18th century and named Helix because it resembled gas-giant planets. The Helix Nebula lies six hundred and fifty light-years away from world Earth. 

Butterfly Nebula

The butterfly nebula is another form of a planetary nebula. The bright clusters of nebulae in the Earth’s night sky are named after flowers and insects. Hence, the NGC 6302 is a planetary nebula which is called the Butterfly Nebula. It is named so because of its wingspan, which covers over three light-years. 

It has a surface temperature of about 2,500,000 degrees Celsius. It is a dying central star that is extremely hot and shines brightly in ultraviolet light. However, it is hidden from the dense amount of dust. 

Saturn Nebula

Saturn Nebula is a planetary nebula that Sir William Herschel in1783 discovered. It is referred to as NGC 7009. It was named Saturn because of the resemblance it had to the planet Saturn with its rings. 

It is a bright star with a dark cavity that is bounded by an oval shape rim. This oval shape rim contains dense red and blue gases.

They are trapped in a green material that is shaped like a barrel. This barrel forms the outer layer of the Saturn Nebula. These stars become cooler and redder as they grow old. Along with these two changes, the star starts increasing its size and energy outputs. Eventually, they are referred to as red giants. 

Dumbbell Nebula 

The dumbbell nebula is referred to as Messier 27 after Charles Messier, who discovered the planetary nebula. The Hubble shows three different colours around the nebula when you look at the Dumbbell Nebula or Messier 27’s images. The three colours represent elements of the nebula. 

The blue is the oxygen, green is the hydrogen, and red is the sulfur and nitrogen. M27 is a host of gases and dust. Their size ranges from seventeen billion and fifty-six billion kilometres. It is much greater than the distance from the sun to Pluto. The mass of a Dumbbell Nebula has as many as three Earths. Dumbbell Nebula is the brightest planetary nebula in the sky. It is found near the constellation Fox (Vulpecula) and can be seen with binoculars.

The term potential energy was introduced in the 19th-century by the Scottish Engineer and Physicist William Rankine, and this concept has a relationship with Greek philosopher Aristotle’s concept of potentiality. Potential energy definition is given as the energy produced when there is an alteration in the form or state of the object. The energy which is stored by an object by the virtue of its position relative to various parts of the system is known as potential energy. 

When a spring is compressed or stretched, it is displaced from its equilibrium position. So, some amount of energy is gained which is stored in the form of stress and can be felt with our hands when we stretch it. 

In terms of Physics, we define potential energy as the energy protected/stored by an object due to its relative position to other objects, which it stresses/saves within itself, its electric charge, or other factors like energy. 

Potential Energy Examples

Below are some potential energy examples which illustrate the real-life applications of potential energy. Here the relationship between the potential energy and kinetic energy is also explained very well:

• Water at the top of the waterfall stores energy (which is the potential energy) and that energy helps rotate the turbine and convert its kinetic energy into electricity. 

• A rubber band is an application of Newton’s first law of motion or the law of inertia. Now, as you apply force on it, it stretches and enlarges by length. It is because the molecules inside the rubber band had initially stored energy, and when you apply the force, all molecules are set into motion because they gain kinetic energy. Eventually, they set apart and the band stretches. 

• You take a bow and an arrow, and initially, they both have stored energy. Now, as you stretch the bow, and leave it, the arrow leaves the bow and reaches far away according to the magnitude of force applied by us. So, this stored energy or simply the potential energy gets transformed into kinetic energy by the force of our fingers.

 

Other Potential Energy Examples

• A truck standing at the tip of the mountain has potential energy unless it slides along with the mountain to reach the ground. Now, as the driver starts the truck, the truck utilizes all its stored potential energy to make drag down the ground. 

Potential Energy- Types

Potential energy is classified into different types as follows-

1. Gravitational Potential Energy

2. Elastic Potential Energy

3. Electrostatic Potential Energy

Gravitational Potential Energy

The energy possessed by an object when it is raised to a certain height against the gravity is known as the gravitational potential energy of that object. The gravitational energy is independent of the distance traveled by the object. It depends on the difference between the initial height of the object and its final height, which is the displacement of the object. Therefore, the path taken by the object along which it has reached the height is not taken into consideration. The gravitational potential energy is given by-

W=mgh

Where,

w= work done

m= mass

g= acceleration due to  gravity 

h= height 

Elastic Potential Energy

The energy which is stored in an object which possesses the capability to compress or stretch is known as the elastic potential energy. It is used in trampolines, rubber bands, and bungee cords. The elastic potential energy is greater if the object is more stretched. 

The elastic potential energy of an object in mathematical terms is given by-

[U = frac{1}{2} k x^2 ]

Where the elastic potential energy is represented as U, spring force constant is represented as k, and stretch length of the string is represented by x.

The following objects are specifically designed to store elastic potential energy:

• A twisted rubber band that powers a toy plane/bungee cord.

• A stretchable bow.

• A bent diver’s board just before a diver dives in a river.

• Coil spring of a wind-up clock/generator/motor.

Electrostatic Potential Energy 

Electrostatic potential energy is the energy required to move a charge from one point to another through a potential difference. Mathematically, we can say, 

U=Vq,

Where U is the electrostatic potential energy, V is the potential difference and q is the charge.

 

Potential Energy Units

The potential energy is denoted by U, V, or PE. The SI unit of the potential energy is Joule which is symbolized by an English letter ‘J’. The dimension of potential energy is M1L2T-2.

 

Relation Between Kinetic Energy and Potential Energy

In the last example, we discussed the scenario of a truck going up the tip of the mountain and then going down the mountain to reach the ground.

 

 

So, initially, it had stored energy that is the potential energy, and then it started moving up the mountain, which is the kinetic energy. So, the total energy utilized by it is given as:

 

KEi + PEi 

 

Now, as it is at the tip, and it again has a final stored or potential energy as it starts moving down the mountain, this stored energy transforms to kinetic energy. Now, the total energy used in the final case is as follows:

 

KEf + PEf

 

So, whatever total energy was used initially equals the energy used finally. So, the relationship between kinetic and potential energy is:

 

KEi  + PEi = KEf + PEf

The Universe comprises energy and matters where matter includes particles, namely molecules and atoms. Moreover, the molecules and atoms with the help of energy can move invariably. So, their motion can either be that of colliding with each other or moving forward and backward. 

As a result of this motion between atoms and molecules, heat energy is formed, which is one of the fundamentals of the principles of calorimetry. Furthermore, thermal energy is present everywhere – in the human body, in volcanoes and even in the coolest spaces. It is transferable from one body to another body.

This heat flow that takes place within physical processes and chemical reactions is measurable. Additionally, the procedure of measuring heat is termed calorimetry.

What Is Calorimetry?

To define calorimetry, it can be said that it is an act of quantifying the change in the thermal energy of an object. Some of the vital highlights related to calorimetry are as follows.

• The temperature of a body or an object determines the heat amount present in that body. 

• Temperature and heat energy are directly proportional to each other. So, this means that the more the amount of heat energy the more is the temperature of a body.

• To evaluate the loss and gain of thermal energy, an object’s temperature is measured prior to and after the transfer of heat. Hence, this temperature difference ascertains the heat change of a body. 
  

For example:

Let us consider a hot cup of coffee or chilled ice cream, which is kept at room temperature. Eventually, after an hour or two, the coffee will cool down, and the ice cream will melt. This change happens because the coffee releases heat energy, and its temperature reduces. On the other hand, the ice cream’s temperature rises as it absorbs heat from the atmosphere.

Notably, the process of calorimetry is executed using a calorimeter. A calorimeter is a tool that measures either the quantity of heat energy gained or released or specific heat capacity.

What is the Principle of Calorimetry 

In a calorimeter, two forms of matter (desirably a liquid and a solid) are situated in contact with one another. Moreover, both bodies have distinct temperatures. Due to this arrangement, heat energy gets transferred from an object having a greater temperature to an object having a lesser temperature.

However, heat flow continues until a state of thermal equilibrium is achieved between the bodies. The principle of calorimetry signifies the “law of conservation of energy.” Hence, this statement means that the total amount of heat absorbed by the cold object is equal to the total amount of heat released by the hot object.

Formula Related to Calorimetry

The basic concept of calorimetry is as follows.

The heat released by the hot object = Heat absorbed by the cold object

The transfer of heat is evaluated with the help of a formula, which is as follows

Q = mCΔT

Where Q = Entire heat energy (J)

m = Mass of an object or body (g)

C = Specific heat capacity (J/gm K)

ΔT = Change in temperature (°C)

(Fact: 4.1813 J/gm K is the specific heat capacity of water)

Numericals on Principles of Calorimetry

(i) What is the amount of heat needed to change 1g of water by 40°C. Provided that C of water is 4.2 J/gm K.

Solution: C= 4.2 J/gm K; m= 1g; ΔT= 40, then

According to the equation Q= mCΔT,

Therefore, Q= 1 X 4.2 X 40= 168 Joules.

(ii) 1000J of heat is applied to a mass of lead 0.5kg to change its temperature from 20°C to 40°C. Determine its heat capacity.

Solution: Q= 1000J; m= 0.5kg; ΔT= (40-20)°C= 20°C, then

C= 1000/(0.5X20); C= 100 J/kg K.

Do It Yourself

1. The Study of Calorimetry is Based on Which Law?

(a) Law of Kinetic Energy   

(b) Joule’s Law   

(c) Law of Conservation of Energy   

(d) None

provides the above information. Additionally, for more detailed knowledge on what is calorimetry in Physics, you can even download our app which offers easy access to every related study material and online class.

The principle of calorimetry is a concept taught in 11th class physics. The concept of calorimetry is introduced in chapter 11 in the NCERT book, the chapter is called thermal properties of matter. This chapter is an extremely important part of physics, it explains in depth the notion of heat and temperature and how temperature changes are a part of our day-to-day lives. In the study of physics, it is extremely important to define the notions of heat temperature et cetera. This chapter mainly talks about what really heat is and how it can be measured. It explains the many processes by which the flow of heat takes place from one place to another. This is where the study of calorimetry becomes important.

We know that the universe consists of matter-energy, matter can be further divided into atoms and molecules and The reason why these atoms and molecules are in motion is that the energy makes them in motion. This is either done by vibrating back and forth or by bumping into each other. This movement of the atoms and molecules produces energy that we call thermal energy or heat. Calorimetry mainly deals with the heat transfer that occurs within two objects and this method is known as calorimetry.

The ’s team has done extensive research and tailored The study material on the topic principles of Kalidah Metry according to the needs of the students this article mainly deals with the definition of calorimetry their examples, it explains the principle of calorimetry, formulae related to calorimetry, along with these The ’s team has also given practice questions along with their solutions based on principles of calorimetry so that students can get a good hold over the concept of Calorimetry.

The word calorimetry when divided can be seen as two words where calorie means heat and Metry means measurement, when combined the two words means measurement of heat, therefore, calorimetry can be defined as the measurement of heat in very simple terms. The device by which colorimetry can be measured is called a calorimeter.

A calorie meter is a metallic vessel that also includes a stirrer, both vessel and stirrer are made of the same material which is copper or aluminum. To ensure that there is no heat loss the vessel is kept in a wooden jacket. There is a small opening in the outer jacket through which a mercury thermometer can be inserted.

Important topics discussed in the chapter-

11.1 Introduction

11.2 Temperature and heat

11.3 Measurement of temperature

11.4 Ideal-gas equation and absolute temperature

11.5 Thermal expansion

11.6 Specific heat capacity

11.7 Calorimetry

11.8 Change of state

11.9 Heat transfer

11.10 Newton’s law of cooling

Ptolemy is one of the ancient astronomers from Egypt during the second century A.C and he was considered to be the most important and influential astronomer of antiquity. Egyptians have always been most curious about the earth, space and time. There are many clues and evidence, which explains that people were aware of the universe and most of the Egyptians were capable of recognizing the stars and the planets. Their knowledge of cosmology was found to be accurate and over a period of time, it is found to be fundamental and many advanced civilizations carried it further.

The cosmological model suggested by Ptolemy is known as the Ptolemaic system or Ptolemaic model and the Ptolemaic system is often also referred to as a geocentric system. The term ‘ge’ in Greek means the earth. In the geocentric system or Ptolemaic system, the earth is statically situated at the centre and the rest of the planets are revolving around it, including the sun, which was also considered a planet. In this article, we will have a deep insight into the Ptolemaic system or Ptolemaic model.

Ptolemaic Model

The initial days of astronomy had been extremely painful for the astronomers. It was highly impossible to convince people against their holy thoughts. Around four centuries ago, during the 16th and 17th centuries, the fear of heretics teaching and opinions that contradicted the bible dominated the catholic church. A kind of war between science and religion got into action, but there were a lot of casualties on the side of science. Before we start with the Ptolemaic model or the Ptolemy geocentric model, let us have a brief history of the heliocentric model.

What is the Heliocentric Model?

The word ‘helio’ means the sun and the centric means located at the centre. The heliocentric model or the heliocentric theory suggests that the sun is situated at the centre of the system and the earth is revolving around the sun in a circular orbit. And this was against the catholic church and the holy books.

In his book ‘The Mathematical Collection’, which later renamed and to be called ‘the Almagest’, Ptolemy has described that the structure of the planetary system (Ptolemaic system definition) and the location and position of each star within it which can be referred to even in modern astronomy. In his book, Ptolemy summarizes the activities of centuries of ancient Greek astronomy and also adds a number of new concepts with theoretical and mathematical descriptions.

Ptolemy Geocentric Model:

According to Claudius Ptolemy, the Earth was situated at the centre of the Universe, whose view of the cosmos persisted for more than 1400 years until it was overturned, with controversies by discoveries of Copernicus, Galileo, and Newton. 

Ptolemy is a great astronomer in ancient times based in Egypt who lived in Alexandria back in the early 2nd centuries AC. Under the supervision of Greek rulers, Alexandria cultivated and established a famous library that attracted many scholars and scientists from Greece, and its school for astronomers received generous patronage. After the Romans conquered Egypt during 30 BCE (when Cleopatra got defeated by Octavian), Alexandria became the second huge city in the entire Roman Empire and a major source of Rome’s economy and grain, but less funding was provided for the scientific study of the stars and the planets. 

Ptolemy was the only great ancient astronomer of Roman Alexandria. Ptolemy was not only an astronomer but also he was a mathematician, geographer, and astrologer. Befitting his diverse and versatile intellectual pursuits, he had a motley cultural makeup. Ptolemy lived in Egypt, wrote theories in Greek, and bore a Roman first name, Claudius, indicating he was a Roman citizen, probably a gift from the Roman emperor to one of Ptolemy’s ancestors.

Ptolemy studied, utilised, and synthesized the Greek knowledge and facts of the known Universe, we can call it the Ptolemy view of the universe or Ptolemaic universe. Ptolemy’s work has enabled many astronomers to make accurate predictions of planetary positions and solar and lunar eclipses, promoting acceptance of his view of the cosmos in the catholic and many other religious worlds and throughout Europe for more than 1400 years, which let us know that he has given us a strong foundation for the cosmology. 

Ptolemy accepted Aristotle’s idea of the earth being at a constant position and the Sun and the planets revolving around a spherical Earth, a geocentric view. Later, Ptolemy developed this idea through rigorous observation and gave a mathematical description in detail. During this process of proceeding with the Ptolemy geocentric model, Ptolemy ended up rejecting the hypothesis of Aristarchus of Samos, who visited Alexandria about 350 years before Ptolemy was born. Aristarchus’ hypothesis claimed that the Earth revolves around the Sun, but he could not produce any evidence to back it up. Though it was true due to lack of documentation and proofs he could not convince society.

Ptolemy, based on observations that he made with his naked eye, he was able to witness the Universe as a set of nested, transparent spheres, with Earth in the centre. In the Ptolemy solar system, the only planets that were present are the sun, mars, moon and venus apart from the earth. Because Ptolemy was able to locate the Moon, Mercury, Venus, and the Sun all revolving around the Earth. Beyond the Sun, he thought, Mars, Jupiter and Saturn, the only other planets in our universe and only planets known at the time (as they were visible to the naked eye). Beyond Saturn lay a final and one last sphere with all the stars fixed to it that revolved around the other spheres. And this was known as the Ptolemy geocentric theory.

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This idea of the universe did not fit exactly with all of Ptolemy’s observations and the idea of the Ptolemaic universe. Ptolemy was aware that the size, motion, and brightness of the planets varied from one another. Thus, Ptolemy incorporated Hipparchus’s concepts of epicycles, which was put forth a few centuries earlier, to work out his calculations. Epicycles were considerably small circular orbits around imaginary centres on which the planets were assumed to move while making a revolution around the Earth. 

By using Ptolemy’s tables, astronomers could accurately predict eclipses and the positions and locations of planets. Due to real visible events in the sky seemed to accept and confirm the truth of Ptolemy’s views. Ptolemy’s ideas were accepted for centuries until the Polish and advanced astronomers, such as Copernicus, proposed in 1543 that the Sun, rather than the Earth, belonged in the centre. That began another controversy between the geocentric model and the heliocentric model. 

Did You Know?

Ptolemy’s astronomy is almost based on the Physics of Aristotle which separates the activities of the sub-lunar world (i.e., on the earth) and the supra-lunar world. According to Aristotle, the supra-lunar world is made up of special material or matter that differs from the material on earth. This material is known as ether. Ether is very hard and considered to be a massless material, i.e., lighter than anything known on earth. Ether’s main and significant feature is its circular motion, and thus all the stars, by their nature, move in circles.

In the Ptolemaic system, all-stars move along spheres. These spheres revolve around the earth, but the earth is not always precisely at its centre. According to the Ptolemaic model, each planet has a system of spheres along which it moves. The merging of the circular motions of the planets resul
ts in non-circular motion. Beyond the spheres of the planets, all the stars are positioned within a single sphere. These stars have accurate fixed places in the sphere.

The stars are all positioned within a single sphere and this sphere revolves around the earth and completes an entire revolution every 24 hours (that makes a complete day). Thus, this movement around the earth is also common to the planets, including the sun. The daily revolution around the earth in particular path is added to the various movements of the different planets, each in relation to its own spheres.

What is Radioactivity?

Radioactivity comes under a dangerous phenomenon but is quite useful. It is the phenomenon that opened a door into the world of sub atoms and influenced the beginning of the nuclear revolution. 

Radioactive atoms possess a certain amount of energy and produce electromagnetic waves spontaneously. These emissions are named as radiation. On our earth, many radioactive materials are available naturally. These materials keep our planet warm. Radioactive materials produced cosmic rays continuously into the atmosphere. Nuclear reactors and particle accelerators utilize nuclear materials to produce radioactive material.

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The rate of radioactive element decays can be expressed as a half-life, which means the total time required for one-half the given quantity of isotope.

Radioactivity Beta Decay

Radioactive beta decay can be defined as the property of several elements available naturally along with isotopes produced artificial isotopes of the elements. 

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Radioactive beta decay occurs in the presence of many protons or many neutrons inside the nucleus. One of protons or neutrons can be transformed into a different form. 

The conservation of electric charge is required in this reaction. If a neutral neutron which transforms into proton electrically, another electrically negative particle will be produced. Here, we can depict that an electron can also be generated.

Three primary ways to differentiate this phenomenon are proton decay, neutron decay, and electron decay. Protons can be charged straight to form neutrons and vice-versa by using these three methods.

The atomic number is continuously changing in every single decay so that some different elements, such as parent atoms and daughter atoms, are formed.

This process is a weak interaction decay process. The beta decay is generally of two types. One is beta minus (β-), and the other one is beta plus (β+).

Beta Particles

Beta emitters are harmful to our bodies. A large amount of radiation of beta particles may cause skin burn and erosion. If they enter the body, they will cause some severe health issues. 

These beta particles are generally in the form of electrons or positrons (which are electrons with a positive electric charge).

The emission of the charged particles that flow from the nucleus of a radioactive element during the radioactive decay procedure or disintegration has a mass equal to 1/1837 as compared to the proton. The mass of the beta particle is half of one-thousandth of the mass of a proton. 

These particles carry either a single positive (positron) or negative (electron) charge. These particles can achieve relativistic speed, which is compared to the speed of light. It is possible because they have a small mass and can release high energy.

They lose energy through rapid interaction with matter, so they are lighter in mass. Though they move through air or other materials, their path becomes desultory.

Rather than the alpha particles, beta particles are much less ionized. They do less damage to a given quantity of energy deposition generally. They range from tens of centimeters in the air, which is energy-dependent; however, in the case of materials, it is a few.

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A beta decay process consists of carbon-14. It is used in radioactive dating techniques. The reaction of nitrogen-14 and electron is written below:

614C → 714N + -10e

Usually, the beta emission is denoted by the Greek letter. It is necessary to memorize the whole phenomenon to understand nuclear calculations with this Greek letter without any further notation.

Beta Minus Decay

In this type of decay, a neutron which is present inside the atom’s nucleus converts into a proton in beta minus decay. The electron and antineutron travel from the nucleus, which now has more than one proton before it started. 

Though an atom summons a proton at the time of beta-minus decay, it alters from one element to another. We can take an example as, after the ongoing beta-minus decay, an atom of carbon, which possesses 6 protons, will become an atom of nitrogen with 7 protons.

In this decay, a neutron is converted to yield a proton, making an increment in the atomic number of the atom. Here, a neutron is neutral, but the proton possesses a positive charge.

To make a balance in the conservation of charge, the nucleus produces an electron and an antineutrino in this process. Antineutrino is the antimatter. It is the counterpart of neutrinos. Both of these have less mass and are neutral particles.

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In beta minus decay, the change in atomic configuration is;

ZAX → Z + 1AY + e[^{-}] + v[^{-}]N = p + e[^{-}] + v[^{-}]

The decay of 14C and 14N is the best example of beta minus decay. It usually establishes the neutron-rich nuclei.

Beta Plus Decay

Here, a proton turns into a neutron; a positron and a neutrino inside an atom’s nucleus. Positron and neutrino travel from the nucleus which has less proton than before. Due to the loss of a proton during beta plus decay, it changes to one element from another. Also, conservation of charge takes place. The beta plus decay conservation law also earns a positron and neutrino.

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ZAX → Z – 1AY + e[^{+}] + vN = p + e[^{+}] + v

Beta Emission

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Beta-decay or β decay represents the disintegration of a nucleus to become a daughter through beta particle emission.

The nucleus will lose an electron or positron when a nucleus emits a beta particle. Here, the mass of the daughter nucleus remains constant, and a different element is formed.

Beta particles possess high-energy, high-speed electrons emitted by certain radioactive nuclei like potassium-40. The range of penetration of beta particles is greater than the alpha particles. It still lacks the strength to beat gamma rays. The beta particles emitted are in the form of ionizing radiation, also called beta rays or beta emission.