Photon Energy Calculator
photon energy calculator. Get instant, accurate results. Enter values for instant results with step-by-step formulas.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator
Photon Energy Calculator
Calculator
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Formula: E = hf = hc/λ
Worked example — 2.25 eV
Formula
E = hf = hc/λ
Energy of a photon. h = 6.626×10⁻³⁴ J·s, c = 2.998×10⁸ m/s.
Worked Examples
Example 1: Green light
Problem:λ=550nm
Solution:E=6.626e-34×3e8/550e-9=3.61e-19 J=2.25 eV
Result:2.25 eV
Frequently Asked Questions
What is photon energy and how is it calculated?
A photon's energy is given by E = hf = hc/λ, where h = 6.626×10⁻³⁴ J·s (Planck's constant), c = 2.998×10⁸ m/s (speed of light), and λ is the wavelength. Shorter wavelengths produce higher-energy photons.
How do you convert photon energy between joules and electron-volts?
1 electron-volt (eV) = 1.602×10⁻¹⁹ J. To convert: eV = E(J) / 1.602×10⁻¹⁹. Visible light photons range from about 1.8 eV (red, 700 nm) to 3.1 eV (violet, 400 nm). X-ray photons exceed 100 eV.
What units are used in photon energy calculations?
Wavelength λ is entered in nanometres (nm). Energy is output in both joules (J) and electron-volts (eV). Frequency f is in terahertz (THz = 10¹² Hz). Planck's constant h = 6.626×10⁻³⁴ J·s and c = 2.998×10⁸ m/s are used internally.
What is the photoelectric effect and why does photon energy matter?
In the photoelectric effect, a photon must have energy above the material's work function to eject an electron. For example, zinc has a work function of ~4.3 eV, so UV photons (λ < 290 nm) are needed. This principle underpins solar cells and photodetectors.
How does energy conservation work in physics?
The law of conservation of energy states that energy cannot be created or destroyed, only transformed. In a closed system, total energy remains constant. For example, a falling object converts potential energy (mgh) to kinetic energy (0.5mv^2). At any point, KE + PE = total mechanical energy.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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