Photoelectric Effect Calculator

What Is the Photoelectric Effect?

When light strikes a metal surface, electrons can be ejected if each photon carries enough energy to overcome the material work function. Einstein explained this in 1905 using quantized light energy, a cornerstone of quantum physics.

Photoelectric Equation

The maximum kinetic energy of an emitted electron is:

$$K_{\max} = hf - \phi = h(f - f_0)$$

where:

$h = 6.626 \times 10^{-34}\,\text{J·s}$ — Planck constant
$f$ — incident photon frequency (Hz)
$\phi = hf_0$ — work function (energy needed to free an electron)
$f_0$ — threshold frequency below which no electrons are emitted

The stopping potential that halts the fastest electrons is:

$$V_{\text{stop}} = \frac{K_{\max}}{e}$$

Related tools: Photon Energy Calculator and Bohr Model Calculator.

Frequently Asked Questions

Why is there a threshold frequency?

Each photon must supply at least the work function energy. Below the threshold, individual photons cannot free electrons regardless of light intensity.

Does brighter light always eject faster electrons?

No. Brightness increases the number of photons, not the energy per photon. Electron speed depends on frequency, not intensity.

What is a typical work function?

Sodium is about 2.3 eV. Copper is near 4.7 eV. UV light is often needed for metals with higher work functions.

How is stopping potential measured?

A variable reverse voltage is applied until the photocurrent drops to zero. That voltage equals the maximum kinetic energy divided by the electron charge.

Can I use wavelength instead of frequency?

Yes. Frequency equals speed of light divided by wavelength. This calculator accepts either input and converts automatically.

Report

What Is the Photoelectric Effect?

Photoelectric Equation

Frequently Asked Questions

Related Tools

Recent Visits