Photon energy and frequency are linked when we talk about the photoelectric effect.

So, what does that mean?

Basically, the energy of a photon (which is a tiny particle of light) can be calculated using this equation:

E = h x f

Here’s what those letters stand for:

• E = energy of the photon (measured in joules)
• h = Planck's constant (which is a very small number: 6.63 x 10^-34 Js)
• f = frequency of the photon (measured in hertz)

This equation shows that if the frequency is higher, the energy of the photon is also higher.

Now, let’s talk about metals. For electrons (which are tiny particles in atoms) to be released from a metal, a certain minimum frequency, called the threshold frequency (f₀), is needed.

For example, for sodium metal, this frequency is about 5 x 10^14 Hz.

When light has a frequency above this point, it means the photon energy is high enough to overcome the energy holding the electrons in the metal. This is what allows the photoelectric effect to happen!