eV to Wavelength Calculator
Convert photon energy in electron volts (eV) into wavelength instantly.
What this eV to wavelength calculator does
This calculator converts the energy of a photon from electron volts (eV) to wavelength. It is useful for physics students, optics enthusiasts, electronics engineers, and anyone working with light, spectroscopy, LEDs, lasers, or semiconductor band gaps.
Because photon energy and wavelength are inversely related, higher-energy photons have shorter wavelengths, while lower-energy photons have longer wavelengths.
Core formula used
The calculator uses the standard photon energy relationship:
Rearranged for wavelength:
λ = hc/E
In practical eV-to-nm form:
λ (nm) = 1239.841984 / E (eV)
Where:
- E is photon energy in electron volts (eV)
- λ is wavelength
- h is Planck’s constant
- c is the speed of light
How to use the calculator
- Enter a positive energy value in eV.
- Choose how many decimal places you want.
- Click Calculate Wavelength.
- Read the wavelength in nm, μm, and meters, plus frequency and spectral region.
Quick examples
| Energy (eV) | Wavelength (nm) | Typical Region |
|---|---|---|
| 1.0 | 1239.84 | Near Infrared |
| 2.0 | 619.92 | Visible Red/Orange |
| 2.5 | 495.94 | Visible Blue-Green |
| 3.1 | 399.95 | Violet / Near UV |
| 10.0 | 123.98 | Ultraviolet |
Why this conversion matters
1) Optics and photonics
Designers of optical systems often specify sources by wavelength (nm), while data sheets or physics references may provide energy in eV. A quick converter avoids mistakes.
2) Semiconductor physics
Band gap energies are commonly stated in eV. Converting to wavelength helps estimate the color of emitted light in LEDs or the absorption range in solar materials.
3) Spectroscopy and lab work
Spectra are often measured in wavelength, but transitions can be discussed in energy terms. Moving between these units is fundamental for analysis and reporting.
Common mistakes to avoid
- Using zero or negative eV: photon energy must be positive.
- Forgetting units: this calculator expects eV and returns wavelength primarily in nm.
- Applying to massive particles directly: this equation is for photons.
- Rounding too early: keep enough decimal places for precision work.
Frequently asked questions
Is eV the same as volts?
No. An electron volt is a unit of energy. A volt is electric potential. They are related but not the same unit.
Can I convert wavelength back to eV?
Yes. Use the inverse relation: E (eV) = 1239.841984 / λ (nm).
What visible range should I remember?
A practical visible range is about 380 nm to 750 nm. Shorter is ultraviolet; longer is infrared.
Final note
If you regularly work with lasers, LEDs, spectroscopy, UV sources, or photovoltaic materials, this eV to wavelength calculator can save time and reduce conversion errors. Bookmark it and use it whenever you need quick, reliable photon conversions.