Matter
All matter is made up of atoms. John Dalton was the first scientist who postulated that when the matter is broken down, the smallest entity that can be obtained is an atom. He, however, believed that atom can no further be disintegrated. This wasn’t true as it turned out.
Today, we consider it as a drawback of Dalton’s atomic theory, because atoms are indeed made up of three fundamental particles, namely electrons, protons and neutrons.
Electrons are the subatomic particles that carry a negative charge. Their mass is negligible. They revolve in the orbits surrounding the nucleus of an atom. These orbits are also called shells or energy levels. An electron is usually represented by the letter ‘e’. The charge on an electron is 1.6 × 10-19 C.
Of all the subatomic particles, an electron has the lowest mass of the order of 9.1 ×10 -31 kg, which is approximately 1/1800th of a proton.
Electron Formula
An electron can also be understood in the form of electromagnetic waves. The first attempt to calculate the wavelength of an electron was made by de Broglie.
The momentum of an electron, moving with a velocity v can be written as:
P= mv
Then, the wavelength of an electron (λ) can be calculated using the formula:
λ= h/p
In this equation, h is the Planck’s constant, and p is the momentum of the electron.
h= 6.6 × 10-34 kgm2/s
The formula written above is used to calculate the wavelength of an electron and is known as the de Broglie equation, while the calculated wavelength is called the de Broglie wavelength.
From the formula, it can be interpreted, that an electron having a higher velocity (or momentum) will have a shorter wavelength and vice versa.
Photon Meaning and Formula
In quantum physics, we consider that every electromagnetic radiation is made up of small packets of energy called ‘quanta’. Since light is also an electromagnetic radiation, its beam will also be composed of billions of packets of energy, which are called photons.
In other words, a photon is the tiniest quantum of electromagnetic radiation. It can also be understood as the basic unit of all light that exists around us.
Photons are never static. In a vacuum, they move at a constant speed, which is the speed of light (2.9 × 108 m/s). The speed of light is represented by ‘c’.
According to Einstein, the energy possessed by an electron is equal to the product of its frequency and Planck’s constant. He proved that light is nothing but a flow of electrons. More the number of photons present in a beam of light, greater will be its intensity. He experimentally explained that photons have a dual nature, they can behave both as particles and waves. The main postulate of his theory was that the energy of light is related to its frequency. With the help of his experiments on Photoelectric effect, he was able to derive the value of Planck’s constant which came out to be 6.6 × 10-34 kgm2/s, exactly what Planck had calculated in 1900 through his work on electromagnetic waves.
The energy and momentum of a photon are dependent on its frequency and wavelength, by the equation
E =hc/λ
The important characteristics of photons are as follows:
Photons possess no mass or rest energy. They are only existent as particles in motion.
Despite having no rest mass, they are considered as elementary particles.
Photons do not have any charge.
They are quite stable.
Photons are carriers of energy and momentum, depending on the frequency.
They can interact with other subatomic particles such as electrons.
Photons can be created or destroyed by various natural phenomena, such as absorption or emission of radiation.
They travel with the speed of light in vacuum.
What is the Difference Between Photons And Electrons?
Did You Know?
Not just light, all electromagnetic radiation is composed of photons.
Einstein conceptualized the idea of photons, but the term ‘photon’ was first used by Gilbert Lewis.
A photon can be created or destroyed, but it never decays on its own.
FAQs on Electrons and Photons
1. What are electrons and how are they characterized in the atomic structure?
Electrons are negatively charged subatomic particles that orbit the nucleus of an atom in defined energy levels or shells. They have a negligible mass compared to protons and neutrons, about 9.1 × 10-31 kg, and play a key role in chemical bonding and electrical conductivity.
2. How do photons differ from electrons in terms of properties and behavior?
Photons are quantum particles of electromagnetic radiation, such as light, while electrons are material, negatively charged particles found in atoms. Photons have no mass or charge, always move at the speed of light in a vacuum, and can be created or destroyed. In contrast, electrons have mass, carry a negative charge, and are considered stable components of matter.
3. Explain the concept of the dual nature of light according to modern physics principles.
The dual nature of light refers to the observation that light exhibits both wave-like and particle-like properties. Experiments such as the photoelectric effect reveal light behaving as particles (photons), while interference patterns show its wave nature. This concept is fundamental to quantum physics.
4. What is the de Broglie wavelength associated with an electron, and how is it calculated?
The de Broglie wavelength (λ) of an electron is given by the formula λ = h/p, where h is Planck's constant (6.6 × 10-34 kg·m2/s), and p is the electron's momentum. This means the faster an electron moves, the shorter its wavelength, exhibiting its wave-like property.
5. How is a photon produced during electronic transitions in an atom?
When an electron absorbs energy and moves to a higher energy level (excited state), it later returns to a lower energy state by emitting the absorbed energy as a photon. The energy and frequency of the photon match the energy difference between these levels.
6. Why are photons considered to have zero rest mass, and how does this affect their motion?
Photons have zero rest mass, which is why they always travel at the speed of light in vacuum (approximately 3 × 108 m/s). They only exist when in motion and never at rest, enabling them to transfer energy across space as electromagnetic waves.
7. What practical evidence supports the concept that electrons have both particle and wave properties?
Experiments like electron diffraction and interference patterns in double-slit experiments demonstrate that electrons can behave as waves, producing interference fringes. Additionally, their behavior in electric and magnetic fields confirms their particle nature.
8. How does the energy of a photon depend on its frequency and wavelength?
The energy (E) of a photon is directly proportional to its frequency (ν) via the equation E = hν and inversely proportional to its wavelength (λ) using the formula E = hc/λ, where c is the speed of light and h is Planck's constant.
9. What role do electrons and photons play in the phenomenon of the photoelectric effect?
In the photoelectric effect, when photons of sufficient energy strike a metal surface, they transfer energy to electrons, causing these electrons to be emitted from the surface. This experiment proved the particle nature of light and supported quantum theory.
10. If photons have no charge or mass, how do they transfer energy and momentum?
Photons transfer energy and momentum due to their quantized nature, as described by E = hν and by possessing momentum p = h/λ. This enables them to exert pressure (radiation pressure) and interact with electrons during phenomena such as the photoelectric effect or Compton scattering.
