Atoms are a basic unit of material. According to the Bohr atom model atoms contain a small central core called a nucleus which is full of positive charges. Electrons are round about the nucleus in a particular circle named orbits.
The circular path is maintained by the centripetal force derived from the electrostatic force between the electrons and the nucleus. Radiation is a process of transmission of energy from one object to another through the medium or space. It can be ionizing or non-ionizing, which depends upon the energy of the radiation. Ionizing radiation has an energy of more than 10eV and can ionize the particles in their path. But non-ionizing radiation has not much energy to ionize the particles in their path. Ultraviolet, infrared, visible, and microwave are some examples of non-ionizing radiation.
In particle physics, the elementary particle that has a half-spin value and does not undergo strong attraction is called lepton. Electrons are the first generation of leptons. They are the lightest subatomic particles. Electrons were discovered by the English physicist J.J.Thomson.
He found that while investigating the cathode ray. Atoms contain three particles. They are electrons, protons, and neutrons. They are the basic unit of electric charge and it is a negatively charged particles. The number of electrons and the number of protons is the same on the neutral atom. If the number of electrons is higher than the number of protons then it is called positively charged or negatively charged ions. They are the carrier of electric current. The charge of the negatively charged electron is $\mathrm{1.602176634\times 10^{-19}C}$
It is equal and opposite to that of protons. The mass of the electron is $\mathrm{9.1093837015\times 10^{-31}kg}$. It is only $\mathrm{\frac{1}{1836}}$ of the mass of the proton. Comparing this electron is considered massless. That is why the electron mass is not taken into consideration while calculating the mass number of an atom.
The wavelength of the electron is measured by Louis de Broglie. The wavelength of the electron is,
$$\mathrm{\lambda =\frac{h}{p}}$$
h - Planck's constant $\mathrm{-6.626\times 10^{-34}Js}$
Rest of the mass of the electron is calculated by the use of the Rydberg constant and it is denoted as,
$$\mathrm{m_{e}=\frac{2R_{\infty }h}{c\alpha ^{2}}}$$
c denotes the velocity of light
$\mathrm{\alpha}$ denotes fine structure constant
$\mathrm{R_{\infty }}$ denotes the Rudberg constant
Photon is the basic unit of light. It is a quantum of energy or energy packet in electromagnetic radiation. Albert Einstein explained the fact of discrete energy packets during the transmission of light. And it was first named a photon by Gilbert N.Lewis. They are always in motion and move with the speed of light in a vacuum. All electromagnetic energy is made up of photons. They are always neutral. That is they have no electric charge. They do not decay on their own.
The energy of the photon depends upon the frequency of the electromagnetic radiation. That is, inversely proportional to the wavelength of the radiation. If the wavelength of the radiation is high then the energy of the photon is low. So blue light has more power than red light. The energy of the photon is given by,
$$\mathrm{E=hf}$$
F denotes the frequency of radiation
The characteristics of photons are given below.
They behave both like a wave and particle simultaneously.
They have zero mass and rest energy. That means they exist only as moving particles.
In a Vacuum they move at the speed of light $\mathrm{c=2.9979\times 10^{8}m/s}$.
They have a spin one. So they come under bosons.
They are stable and the energy and momentum depend on the frequency.
They make interactions with electrons like the Compton effect.
During the emission or absorption of radiation they can be destroyed or created.
| Electrons | Photons |
|---|---|
| It is a subatomic particle that is presented in all atoms. | It is an elementary particle that carries energy. |
| It is negatively charged. | And has no electric charge. |
| It has mass so it may be at rest. | Protons have no mass. So it cannot be at rest. |
| Electrons are not moving with the velocity of light. | In a vacuum, the photons are moving at the speed of light. |
| The spin of an electron is half. | The spin of a photon is one. |
| It shows particle nature. | It shows both wave nature. |
In this article the facts about electrons and the formula for the energy of electrons are discussed. The facts about photons and the formula for the energy of the photon are also discussed. The characteristics of photons and the differences between electrons and photons are also discussed in detail.
Q1. What is meant by electrostatic attraction?
Ans. It is a force of attraction or repulsion that occurs between the charged particles of the atom without contact. In this phenomenon, a negatively charged atom or molecule is attracted to the positively charged atom. The repulsive force acts between the likely charged atoms or molecules.
Q2. What is Rydberg's constant?
Ans. It is a fundamental constant of atomic physics that is named after the physicist Johannes Rydberg. It is a constant related to the electromagnetic spectrum of the atom. It describes the wavelength or frequency of spectral lines of the atoms. The value of the Rydberg constant is 10,973,731,56816 per m.
Q3. How are electrons discovered?
Ans. It was discovered by J.J.Thompson. A cathode-ray tube that is sealed at one end contains two electrodes. With the help of a vacuum pump, the pressure inside the tube is reduced to 0.01mm. When a high voltage of about 10,000V is applied to the electrodes, an invisible ray is emitted. This experiment led to the discovery of electrons. He proposed that electrons are constituent particles for all atoms.
Q4. What is the Compton effect?
Ans. When a photon having high energy collides with the target it removes the loosely bound electrons from the outer shell of the atom. The wavelength of the scattered radiation is different from the incident radiation. Thus the colliding photon transfers some energy to the electron to recoil it. The angle of scattered photons depends on the energy lost for the recoiling of electrons.
Q5. What are the differences between photons and subatomic particles?
Ans.
| Photons | Subatomic Particles |
|---|---|
| These are energy packets and do not have mass. | Subatomic particles have definite mass. |
| They are moving at the speed of light in a vacuum. | They do not move with the speed of light. |
| They are neutral. | They have charges. |
| They behave like both particles and waves. | They behave like wave particles. |
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