Work and the Quantum Physics Work Function

Work, generally, in physics is a measure of the transfer of kinetic energy. Like water hitting blades in a dam turbine (kinetic energy making electrical force energy). Or when a wagon is pushed to make it go faster (muscle force energy making kinetic energy).

The “work function” is a quantum physics term for a photon hitting an electron and knocking it right off the metal plate, or maybe just knocking the electron from a lower shell in an atom to to higher shell in that atom.

Photons (with analogy to more force) are those of shorter wavelengths. Photons of longer wavelengths, no matter how many are thrown at the atom, will never knock an electron clean out of the surface, or even to a higher shell in the atom.

One pint of water over the dam, will never make one watt of electrical power, even if you drop a pint every day for a century.

One toddler baby finger push on a wagon will never make the wagon go faster if it has any real weight in it.

You can’t do regular physics work with tiny amounts of force. And long wavelength photons can’t do any quantum level work either — they are too weak.

Regular physics Work = Force (in Newtons) times distance (in meters).

A moving pool ball hits another pool ball — 6 Newtons of force for half a meter = 3 Joules of kinetic energy transferred.

Switching over now to the quantum level E = hf The energy of a photon is h (Planck’s Constant times the frequency).

So the higher the frequency (shorter the wavelength) the more energy E the photon has.

If it is too low frequency (long wavelength) it will not do any work at all. It won’t knock electrons out of their atoms, or even to a higher shell within their atoms.

The kinetic energy of photoelectrons is not Newtons times meters, its Plank (h) times the frequency. High frequency electrons do lots of quantum work. Low frequency don’t do any, no matter how many you send.

In an atom the least tightly bound electron (the one you can knock out easiest) determines the “Work Function” of that material (Iron, Silver, Titanium, Steel, Gold, Tin etc). When your photon knocks out that least tightly bound electron it will fly off the surface with K-max + phi (the minimum work needed to free the least tightly bound electron).

So hf = K-max + phi

The incident photon energy Planck(h) times frequency = Kmax (the most kinetic energy of the freed electron) plus phi (the minimum work needed to free that electron).

To make the photoelectric effect happen the incident photons have energy E.

The electrons that fly off the metal will have energy Kmax + phi

Fluorescence is like photoelectric. With the infra red you get none. With regular light you get Balmer series or Paschen series. And with UV light or hard UV light you get Lyman Series (high energy and many photons — bright fluorescent effect).

I use the CCD plates to detect my fluorescent photons, like the astronomy people use. So every one is a “count”, and contributes to the peaks profile array of detected light.

RFG 6 July 2025 written at Hagerstown MD USA