Photon Energy Calculator – Calculate Energy of a Photon
Calculate the energy of a photon from its wavelength or frequency. Our calculator provides results in Joules and electron-volts (eV).
Choose input mode
Select whether you want to calculate from wavelength or frequency.
Enter your value
For wavelength, enter in meters (use scientific notation like 500e-9 for 500nm). For frequency, enter in Hz.
Click Calculate Energy
The calculator uses Planck's equation to compute photon energy in Joules and electron-volts.
| Type | Wavelength Range | Frequency Range | Energy Range (eV) |
|---|---|---|---|
| Radio waves | > 1 mm | < 300 GHz | < 0.0012 |
| Microwaves | 1 mm - 25 μm | 300 GHz - 12 THz | 0.0012 - 0.05 |
| Infrared | 25 μm - 740 nm | 12 THz - 405 THz | 0.05 - 1.7 |
| Visible light | 740 - 380 nm | 405 - 790 THz | 1.7 - 3.3 |
| Ultraviolet | 380 - 10 nm | 790 THz - 30 PHz | 3.3 - 124 |
| X-rays | 10 nm - 0.01 nm | 30 PHz - 30 EHz | 124 - 124,000 |
| Gamma rays | < 0.01 nm | > 30 EHz | > 124,000 |
What Is a Photon?
A photon is a particle of light — the smallest possible packet of electromagnetic energy. Photons have no mass but carry energy proportional to their frequency. Higher frequency means higher energy. This is why ultraviolet light can damage skin while radio waves pass through harmlessly.
Planck's Equation
Photon energy is calculated using E = hf, where h is Planck's constant (6.626 × 10⁻³⁴ J·s) and f is frequency. When using wavelength instead: E = hc/λ, where c is the speed of light (3 × 10⁸ m/s). These equations link the wave and particle nature of light.
Why Use Electron-Volts?
Photon energies are tiny in Joules — typically 10⁻¹⁹ or smaller. Electron-volts (eV) give more manageable numbers. One eV equals 1.602 × 10⁻¹⁹ Joules. Visible light photons have energies of 1.7 to 3.3 eV, much easier to work with than 10⁻¹⁹ J.
Photoelectric Effect
Calculate whether photons have enough energy to eject electrons from a material. This principle powers solar cells and photodetectors.
Spectroscopy
Identify elements by the photon energies they emit or absorb. Each element has a unique spectral fingerprint.
LED Design
The bandgap energy of semiconductor materials determines the photon energy and thus the color of emitted light.
Medical Imaging
X-ray and gamma ray photon energies determine tissue penetration and image quality in medical diagnostics.
What is the energy of a visible light photon?
Visible light photons range from about 1.7 eV (red, 740nm) to 3.3 eV (violet, 380nm). Green light at 550nm has approximately 2.25 eV of energy.
How do I convert wavelength to frequency?
Use f = c/λ, where c is the speed of light (3 × 10⁸ m/s) and λ is wavelength in meters. A 500nm photon has frequency f = (3 × 10⁸) / (500 × 10⁻⁹) = 6 × 10¹⁴ Hz.
Why does blue light have more energy than red light?
Blue light has shorter wavelength and higher frequency than red light. Since energy is proportional to frequency (E = hf), higher frequency means higher energy per photon.
What is Planck's constant?
Planck's constant (h) is a fundamental physical constant: 6.62607015 × 10⁻³⁴ J·s. It relates photon energy to frequency and appears throughout quantum mechanics.
How many Joules is 1 eV?
One electron-volt equals 1.602176634 × 10⁻¹⁹ Joules. This is the energy gained by an electron accelerated through a potential difference of 1 volt.
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