Calculator
Formula used
- E = h f where E is photon energy and f is frequency.
- f = c / λ where λ is wavelength.
- Combining both: E = h c / λ.
- Energy conversion: E(eV) = E(J) / e, with e = 1.602176634×10⁻¹⁹ J per eV.
How to use this calculator
- Select a mode: start from frequency, wavelength, or energy.
- Enter the matching value and choose its unit.
- Optionally enable custom constants for specialized contexts.
- Press Calculate to see energy, frequency, and wavelength.
- Use the download buttons to export your last result.
Example data table
| Input | Value | Derived frequency (Hz) | Derived wavelength (nm) | Energy (eV) |
|---|---|---|---|---|
| Wavelength | 532 nm | ≈ 5.64×1014 | 532 | ≈ 2.33 |
| Wavelength | 1550 nm | ≈ 1.93×1014 | 1550 | ≈ 0.80 |
| Frequency | 500 THz | 5.00×1014 | ≈ 600 | ≈ 2.07 |
| Energy | 1 keV | ≈ 2.42×1017 | ≈ 1.24 | 1000 |
Accurate conversions support clearer physics calculations every single time.
Professional article
1) Why Planck’s relation matters
Planck’s relation links microscopic quantum behavior to measurable waves. It states that photon energy increases linearly with frequency, so higher-frequency light carries more energy per photon. This is central to photoelectric emission, spectroscopy, lasers, solar cells, and radiation safety calculations across science and engineering.
2) Constants and their practical meaning
The calculator uses the SI-defined Planck constant h = 6.62607015×10⁻³⁴ J·s and the exact speed of light c = 299792458 m/s. These values ensure consistent results when converting between frequency (Hz), wavelength (m), and energy (J or eV) for reporting and lab work.
3) From wavelength to energy: common benchmarks
In optics, wavelength is often the starting point. Green laser light at 532 nm corresponds to an energy near 2.33 eV, while telecom light at 1550 nm is near 0.80 eV. These values help compare detector sensitivity, bandgaps, and absorption across materials and devices.
4) Frequency scales used in modern systems
Visible light spans roughly 400–700 nm, which corresponds to approximately 7.5×10¹⁴ to 4.3×10¹⁴ Hz. Ultraviolet pushes higher, increasing photon energy and the likelihood of photochemical reactions. Infrared shifts lower in frequency, supporting thermal imaging and fiber communications.
5) Electronvolts versus joules
Electronvolts are convenient for atomic and solid-state physics because typical electronic transitions are on the order of a few eV. The calculator converts using 1 eV = 1.602176634×10⁻¹⁹ J, letting you move between engineering units (joules) and spectroscopy-friendly units (eV) without manual steps.
6) X-rays and high-energy photons
For higher energies, frequency becomes extremely large and wavelength becomes very small. A photon of 1 keV corresponds to a wavelength around 1.24 nm, in the soft X-ray range. Such calculations support instrument design, shielding decisions, and interpretation of diffraction or absorption data.
7) Data quality and unit discipline
Accurate results depend on consistent units and meaningful significant figures. Choose a unit that matches the measurement context: THz for optical frequencies, nm for laboratory wavelengths, and eV/keV for spectroscopy. Avoid mixing prefixes (kHz with nm, for example) unless you intentionally convert through the calculator.
8) Using results in real workflows
After computing values, export CSV for spreadsheets or PDF for lab notebooks and reports. For experiments, record the input mode, the constants used, and the output in both base SI and practical units (e.g., nm and eV). This improves traceability, peer review, and replication across teams and instruments.
FAQs
1) What is Planck’s relation?
It states E = h f, meaning photon energy equals Planck’s constant times frequency. Higher frequency light has higher energy per photon.
2) Why does wavelength change when frequency changes?
For electromagnetic waves in vacuum, c = f λ. If frequency rises, wavelength must decrease to keep the product equal to the speed of light.
3) When should I use eV instead of joules?
Use eV for atomic transitions, bandgaps, and spectroscopy because values are typically a few eV. Use joules for macroscopic energy accounting and SI-only reports.
4) Does the calculator assume vacuum or a material?
It assumes vacuum using the standard speed of light. In materials, the wave speed changes, so wavelength inside the medium differs even when frequency stays the same.
5) Can I override constants for special cases?
Yes. Enable custom constants to input your own h or c values, useful for teaching, sensitivity checks, or hypothetical scenarios.
6) Why do my results appear in scientific notation?
Photon energies and frequencies can be extremely large or small. Scientific notation keeps values readable and reduces rounding mistakes during interpretation and reporting.
7) What input should I trust most in experiments?
Use the quantity you actually measured. For lasers, wavelength is common; for RF systems, frequency. Enter that value, then export outputs to document derived quantities.