Excitation and Ionisation

Summary

This video introduces the electron volt (eV), explaining its importance in quantum physics for measuring small energies. It defines the electron volt as the work done when an electron moves across a 1-volt potential, equaling 1.6 × 10⁻¹⁹ joules. The video also covers ionization and excitation, explaining how atoms can become ionized by radiation or electric currents, and how electrons can be excited to higher energy levels, leading to phenomena like fluorescence. The electron volt is vital for understanding these processes, especially in fields dealing with atomic and subatomic energies.

Takeaways

• 😀 The electron volt (eV) is a unit used to measure very small amounts of energy in particle and quantum physics.
• 😀 1 electron volt is defined as the work done when an electron is accelerated by a 1-volt potential difference, equal to 1.6 × 10^-19 joules.
• 😀 To convert from joules to electron volts, divide by 1.6 × 10^-19; to convert from electron volts to joules, multiply by 1.6 × 10^-19.
• 😀 Larger units such as kilo-electron volts (keV), mega-electron volts (MeV), and giga-electron volts (GeV) are also used in physics.
• 😀 Ionization is the process in which an atom loses or gains electrons, resulting in a charged particle (ion).
• 😀 Gamma radiation or electric currents passing through gases can ionize atoms by knocking electrons out of their orbits.
• 😀 Excitation occurs when electrons in a gas are energized by external electrons, causing the atom's electrons to move to higher energy levels without being completely knocked out.
• 😀 The energy required for excitation depends on the atom, and each element has specific excitation energies for its electrons.
• 😀 For example, mercury atoms require 4.9 electron volts to excite their electrons to a higher energy level.
• 😀 Fluorescent tubes work by using excitation and ionization processes, where excited electrons eventually relax and release photons, producing light.

Q & A

What is the definition of an electron volt (eV)?

An electron volt (eV) is the amount of energy gained by an electron when it is accelerated by a potential difference of 1 volt. It is equal to 1.6 × 10⁻¹⁹ joules.

How is energy measured in particle and quantum physics?

In particle and quantum physics, energy is typically measured in electron volts (eV), as these energies are very small compared to those in everyday physics, where units like joules or kilowatt-hours are more commonly used.

Why do physicists prefer to use the electron volt instead of joules in particle physics?

Physicists prefer to use the electron volt (eV) in particle physics because the energies involved are much smaller than those in classical physics, making eV a more convenient and practical unit for these small scales.

What is the conversion factor between joules and electron volts?

To convert from joules to electron volts, divide the energy in joules by 1.6 × 10⁻¹⁹. To convert from electron volts to joules, multiply the energy in electron volts by 1.6 × 10⁻¹⁹.

What is the relationship between larger units like keV, MeV, and GeV and the electron volt?

Larger units like kiloelectron volts (keV), megaelectron volts (MeV), and gigaelectron volts (GeV) are simply multiples of the electron volt. One keV is 1,000 eV, one MeV is 1 million eV, and one GeV is 1 billion eV.

What is ionization, and how does it occur?

Ionization is the process where an atom gains or loses electrons, resulting in the formation of an ion. This can occur through gamma radiation or the flow of electric current, such as in fluorescent tubes.

What are positive and negative ions, and how are they formed?

A positive ion is formed when an atom loses electrons, resulting in an imbalance of charge. A negative ion is formed when an atom gains extra electrons. Both types of ions are created during the process of ionization.

What is the difference between ionization and excitation in atoms?

Ionization occurs when an electron is completely knocked out of an atom, whereas excitation happens when an electron is moved to a higher energy level within the atom, but does not leave the atom.

How does excitation work in a fluorescent tube?

In a fluorescent tube, if the electrons flowing through the tube have enough energy, they can excite the atoms of mercury gas, raising the energy levels of the electrons in those atoms. The tube will then light up as the excited electrons return to their ground state and release photons.

What happens to excited electrons after they have been moved to a higher energy level?

After electrons are excited to a higher energy level, they eventually return to their ground state. As they do, they release energy in the form of photons, which is responsible for the light emitted by sources like fluorescent tubes.