This article explains the differences between magnets, PEMF, red light, infrared, and TENS using simple physics concepts, so you can understand how each works without needing a scientific background.
Magnets vs PEMF vs Red Light, Infrared and TENS
Magnets vs PEMF vs Red Light, Infrared and TENS: What Is Actually Different from a Physics Perspective?
When people compare magnets, PEMF, red light, infrared, and TENS, they are usually asking one question in different ways: which goes deeper, which is stronger, or which is more powerful? But from a physics perspective, those questions often mix completely different quantities. This is why pages like magnetic therapy research and How Q Magnets Work matter early in the discussion. A changing magnetic field can generate an electrical effect called electromotive force (EMF). From this point onward, it will be referred to as EMF. Also see, Magnetic Therapy.
Static magnets, PEMF, red light, infrared, and TENS are not versions of the same therapy. Static magnets are static field devices. PEMF is a pulsed induction-based magnetic modality. Red and infrared are photon-based energy therapies. TENS is an electrical stimulation modality.
The problem with most comparisons
A lot of confusion begins when people compare units that do not describe the same thing.
Gauss or tesla describe magnetic field strength. Joules describe energy. Watts describe power. Volts describe electric potential. Milliamps describe current. So asking how many gauss equal how many joules is like asking how many kilograms equal a kilometre. The numbers may sound comparable, but the physical quantities are not. For PEMF, the comparison is even more misleading, because For PEMF, what matters is not just how strong the magnetic field is, but the fact that it changes over time. It is the fact that the magnetic field changes with time, so induction becomes part of the mechanism. Faraday’s law explains that when a magnetic field changes over time, it can generate a small electrical effect (electromotive force, or EMF) in nearby tissue.
Electromagnetic spectrum showing how different types of waves vary in wavelength and frequency, including the visible light range within the broader spectrum. Source: iStock (licensed image)
1. Four Very Different Physical Mechanisms
Static Magnetic Field (Q Magnets)
- Physical quantity: Magnetic flux density
and field gradient ∇ - Units: Tesla (T) or Gauss (G)
- Nature: Static field (non-oscillating)
- Frequency: 0 Hz
- Energy delivery: None in the direct sense used for light, TENS, or PEMF
- Governing concept: Force and torque on moving charges, currents, and dipoles; field gradients matter
- Useful physics: F = q(v × B)
A static magnet is exactly that: static. It does not pulse, it does not oscillate, and it does not have adjustable frequency. Its frequency is effectively 0 Hz. That matters because it means the magnet is not working through time-varying induction in the way PEMF does.
What a static magnet creates is a continuous local field environment. In practical terms, that is one reason non-powered static magnetic devices can be applied simply and worn during the day. They are better described as creating a subtle, sustained local field effect than as delivering an active energy session. In Q Magnets language, the practical question becomes Field | Dose | Placement rather than power output.
PEMF
- Physical quantity: Time-varying magnetic flux density
, magnetic flux 
, and induced electric field - Units: Tesla (T) or Gauss (G), plus frequency in Hz
- Nature: Pulsed magnetic field
- Frequency: Adjustable
- Energy delivery: Yes, as a powered induction-based modality
- Governing law: Faraday’s law:
Because the magnetic field changes over time, PEMF operates through electromagnetic induction. This means it can generate small electrical effects in tissue, as described by Faraday’s law. This time variation is not a minor detail, it is a core part of how PEMF works.
That is why both field strength and pulse frequency matter. Two PEMF devices may quote similar field strengths, but if the pulse frequency, waveform, rise time, or pulse width differ, the induced effect can also differ.
So the correct comparison is not:
“Static magnets vs PEMF: which has more gauss?”
It is:
“Static magnets create a continuous field with no frequency. PEMF creates a time-varying field, so both field strength and frequency become part of the mechanism.”
Red / Infrared Light
Electromagnetic radiation formula showing the relationship between photon energy, frequency, and wavelength (E = hf = hc/λ). Source: AP Physics 2 – Quantum Physics Introduction (2015)
- Physical quantity: Electromagnetic radiation
- Units: W/cm², Joules/cm²
- Nature: Oscillating electric and magnetic waves
- Frequency: Non-zero; related to wavelength
- Energy delivery: Yes, photons deposit energy
- Governing equation:
Light delivers energy into tissue.
Its frequency is built into the wavelength. Shorter wavelength means higher frequency and higher photon energy. Longer wavelength means lower frequency and lower photon energy.
So when comparing light to magnets, the main difference is that light is an energy-delivery wave phenomenon, while a static magnet is a field phenomenon and PEMF is an induction phenomenon.
Blue Light
Same basic physics as red light, but with shorter wavelength and higher photon energy:
Higher energy per photon, but typically shallower penetration because absorption and scattering increase.
TENS / Electrotherapy
- Physical quantity: Electric current
, voltage 
- Units: mA, Volts
- Nature: Pulsed electrical stimulation
- Frequency: Adjustable
- Energy delivery: Yes
- Governing law: V = IR
Or more practically in tissue:
TENS pushes charge through tissue.
Impedance determines current flow.
Like PEMF, TENS has frequency. Like light, it is an active powered modality. But unlike PEMF, TENS is delivering current directly through electrodes rather than inducing electric fields via a changing magnetic field.
2. The First Big Clarification: Gauss Cannot Be Compared to Joules
This is like asking:
How many kilograms is a kilometre?
They measure different dimensions.
- Gauss (magnetic field strength) = field intensity
- Joule = energy
- Watt = power (energy per second)
A static magnetic field does not automatically deliver energy.
Work is defined as:
Diagram illustrating the relationship between force, displacement, and work when force acts in the direction of motion. Source: Virtual Nerd, n.d., “Force and Displacement in the Same Direction”
If there is no displacement (d = 0), no work is done.
This is critical.
A static magnet sitting on the skin is not “injecting energy” into tissue.
It is imposing a field environment.
3. Why Frequency Changes the Comparison
A static magnet has no frequency. It is a continuous field with 0 Hz time variation.
A PEMF device has an adjustable pulse frequency. That frequency is not a side detail. It is part of the mechanism.
A light therapy device also has frequency, because electromagnetic radiation has frequency inherently related to wavelength.
A TENS device has adjustable pulse frequency as part of how stimulation is delivered.
So when people compare PEMF to static magnets, the most important difference is not simply “stronger versus weaker.” It is static versus pulsed.
That also means PEMF is not fully described by field strength alone. A PEMF device is commonly discussed in terms of both:
- Tesla / gauss for field strength
- Hertz for pulse frequency
Static magnets have the first quantity, but not the second. That is a major physics separation.
So What Does a Static Magnetic Field Do?
Magnetic force on a moving charge:
Diagram illustrating Fleming’s right-hand rule, showing the relationship between magnetic field, current, and force directions. Source: IStock / F fridas (2020), licensed image
The key here is gradient.
Uniform fields produce little translational force.
Field gradients produce force.
This is why multipolar magnets matter.
Not north vs south.
Not “energy”.
Gradient.
4. Depth: What Does “Penetration” Actually Mean?
When we say a QF28-6 penetrates 50 mm, what does that mean?
It means:
At 50 mm distance, the field strength is indistinguishable from Earth’s ambient field (~50 microtesla).
It does NOT mean therapeutic threshold extends to 50 mm.
The true biological threshold for static magnetic field response is not precisely known.
Some in vitro data suggests cellular effects at:
- 1–10 mT
- Possibly lower in some contexts
- Possibly higher in others
The honest position is: The field does not extend beyond 50 mm at levels higher than the Earth’s magnetic field. The biologically meaningful threshold is almost certainly less than that distance.
5. Red Light Depth (The 3 cm Claim)
Red light penetration depends on:
- Wavelength
- Tissue optical properties
- Power density
- Time
Typical therapeutic red light (630–660 nm):
- Effective penetration: ~5–15 mm
- Near infrared (800–850 nm): penetration possibly 20–30 mm under ideal conditions
But optical penetration is not equal to uniform therapeutic dose.
Light attenuates exponentially.
Where:
- μ = absorption coefficient
- x = depth
Light deposits energy.
Magnets do not attenuate exponentially in the same way, their field decays with distance differently.
A very different decay profile.
6. Impedance and TENS
TENS depends heavily on tissue impedance.
Fat, dry skin, and bone increase impedance.
Current flow changes dramatically with hydration and electrode placement.
A static magnetic field is not affected by impedance in the same way because it does not require current flow through tissue.
It simply exists in space.
7. Energy vs Force vs Environment
Here is the clean comparison:
| Feature | Static Magnetic Field (Q Magnets) | PEMF | Red / Infrared Light | TENS / Electrotherapy |
| Primary physical quantity | Magnetic flux density (B) | Time-varying magnetic field (B(t)), magnetic flux (ΦB), induced electric field | Electromagnetic radiation | Electric current (I), voltage (V) |
| Common units | Tesla (T), Gauss (G) | Tesla (T), Gauss (G), Hz | W/cm², J/cm², wavelength | mA, Volts, Hz |
| Nature | Static field | Pulsed magnetic field | Oscillating electromagnetic wave | Pulsed electrical current |
| Frequency | 0 Hz | Adjustable pulse frequency | Inherent wave frequency linked to wavelength | Adjustable pulse frequency |
| Main governing formula | F = q(v × B) | ε = − dΦB / dt | E = hf = hc / λ | V = IR I = V / z |
| What enters tissue | Magnetic field | Magnetic field plus induced electric field | Photons | Electrical current |
| Energy delivery | No direct energy delivery | Yes, powered induction-based modality | Yes, photons deposit energy | Yes, electrical stimulation |
| What most differentiates it | Static, non-powered, wearable, sustained | Pulsed, frequency-dependent, induction-based | Wavelength-dependent energy delivery | Electrode-driven current flow |
| Best plain-English description | Field device | Pulsed induction device | Light energy device | Electrical stimulation device |
The magnet is not an energy device.
It is a field device.
8. What Does This Mean Clinically?
Light therapy:
- Works via photobiomodulation
- Alters mitochondrial chromophores
- Delivers measurable energy
TENS:
- Stimulates nerves electrically
- Modifies pain signalling
- Energy dependent
Static magnetic fields:
- Modify charged particle dynamics
- Influence ion channel behaviour
- Potentially alter resting membrane potential (RMP)
- Field gradient dependent
The mechanism space is different.
Which is “better”?
Wrong question.
Which is appropriate for:
- Acute inflammation?
- Chronic degenerative joint?
- Neuropathic pain?
- Superficial tissue?
- Deep joint?
That is the intelligent discussion.
9. The Honest Depth Comparison
“Can Magnets penetrate deeper than light?” Yes, but…
- Light deposits energy and attenuates exponentially.
- Magnetic fields extend through tissue without needing energy delivery.
- Field strength decreases with distance.
- The biologically relevant threshold distance is not precisely defined.
10. The Real Differentiator
Static magnetic therapy is:
- Passive
- Continuous
- Wearable
- Non-energy delivering
- Field gradient dependent
- Not impedance dependent
- Not time dose dependent in the same way as light
Light and TENS are:
- Active
- Time limited
- Energy dependent
This is not a competition.
It is physics.
Conclusion: Don’t Compare Units That Don’t Match
Gauss is not Joules.
Tesla is not Watts.
A static field is not energy.
And work requires displacement.
No movement → no work.
What static magnets do is create a field environment.
And biology responds to environments.
Author & Medical Review
This article was written by James Hermans and independently reviewed by Dr Liisa Laakso.
Dr Laakso is a qualified physiotherapist and researcher with a background in evidence-based healthcare. For more information, view her full bio here: Dr. Laakso
