Describe the photoelectric effect.

  • Google+ icon
  • LinkedIn icon

If we give a peice of gold negative charge and shine long wave, low frequency, electro-magnetic (E-M) radiation on it (for example radio waves) absolutely nothing will happen.

If you start to shorten the wavelength and therefore increase the frequency of the E-M radiation a point will come where the gold will discharge.  This is called the threshold frequency.

This occurs because the raditation is causing negatively charged electrons to leave the gold thereby discharging it.

Let me explain, E-M radiation can manifest itself in the form of particles of light called photons, each photon is a discrete packet of energy. The energy of the photon is directly proportional to the frequency of the radiation according to the equation:

E = hf

where E is energy of the photon, f is frequency and h is a constant.

When the E-M radiation is shone onto the gold, the photons collide with the electrons in the metal and transfer their energy to the electrons. When the frequency of the wave is above the threshold frequency, the photons contain enough energy that when they collide with the electrons, the electron has enough energy to escape the attraction of the gold's nucleus leaving the gold without its negative charge. The energy barrier the electron must overcome to leave the gold is called the potential well.

Umar S. A Level Maths tutor, A Level Physics tutor, GCSE Maths tutor,...

About the author

is an online A Level Physics tutor with MyTutor studying at University College London University

Still stuck? Get one-to-one help from a personally interviewed subject specialist.

95% of our customers rate us

Browse tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss