Cyclotron frequency formula

Explore the cyclotron frequency formula, its significance, and applications in particle accelerators, plasma physics, and MRI.

Understanding Cyclotron Frequency Formula

Cyclotron frequency is a fundamental concept in physics, with applications in various fields such as particle accelerators, plasma physics, and magnetic resonance imaging. This article aims to provide an overview of the cyclotron frequency formula and its significance.

Concept of Cyclotron Frequency

Cyclotron frequency refers to the frequency at which charged particles, like electrons and ions, revolve around a magnetic field when subjected to a uniform magnetic field perpendicular to their velocity. The motion of these particles in a magnetic field is governed by the Lorentz force, which causes them to move in a circular path. The time it takes for these particles to complete one full revolution is called the cyclotron period, and its reciprocal is the cyclotron frequency.

The Cyclotron Frequency Formula

The cyclotron frequency formula is derived from the balance of centripetal force and the Lorentz force acting on the charged particle. Mathematically, it is represented as:

fc = (qB) / (2πm)


  • fc is the cyclotron frequency,
  • q is the charge of the particle,
  • B is the strength of the magnetic field, and
  • m is the mass of the particle.

This formula shows that the cyclotron frequency is directly proportional to the charge and magnetic field strength and inversely proportional to the mass of the particle. It is important to note that the formula assumes the particle’s speed is much less than the speed of light, which ensures the relativistic effects are negligible.

Applications of Cyclotron Frequency

The concept of cyclotron frequency has various applications across multiple domains. Some of these include:

  1. Particle Accelerators: Cyclotrons are a type of particle accelerator that uses the cyclotron frequency to accelerate charged particles to high energies, enabling scientists to study the properties of subatomic particles and their interactions.
  2. Plasma Physics: In plasma physics, the cyclotron frequency plays a crucial role in determining the behavior of charged particles within a plasma, such as the stability and confinement properties of the plasma.
  3. Magnetic Resonance Imaging (MRI): In the field of medical imaging, the cyclotron frequency is utilized in the process of magnetic resonance imaging (MRI). The resonance condition between the applied radiofrequency and the cyclotron frequency of protons in the body is exploited to generate detailed images of the internal structures and tissues.

In conclusion, the cyclotron frequency formula is a fundamental equation in physics, with applications in a wide range of fields. Understanding the underlying concepts and significance of this formula enables researchers and engineers to develop advanced technologies and contribute to the growth of scientific knowledge.

Example of Cyclotron Frequency Calculation

Let’s consider an example to illustrate the calculation of cyclotron frequency for a positively charged particle, such as a proton, moving in a magnetic field.


  • Charge of a proton, q = +1.6 x 10-19 C
  • Mass of a proton, m = 1.67 x 10-27 kg
  • Magnetic field strength, B = 0.5 T

We will now use the cyclotron frequency formula to calculate the frequency:

fc = (qB) / (2πm)

Substitute the given values into the formula:

fc = ((1.6 x 10-19 C) x (0.5 T)) / (2π x 1.67 x 10-27 kg)

Now, perform the calculation:

fc ≈ 2.42 x 107 Hz

Thus, the cyclotron frequency for a proton in a magnetic field of 0.5 T is approximately 2.42 x 107 Hz.

This example demonstrates how to apply the cyclotron frequency formula to calculate the frequency at which a charged particle revolves around a magnetic field. By understanding this calculation, one can better appreciate the applications and significance of cyclotron frequency in various fields.

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