Describe the photoelectric effect.

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.

Answered by Umar S. Physics tutor

3857 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

What is gravitational potential and how can gravitational potential energy be used to estimate the escape velocity of a planet of mass m and radius r?


An ice cube with a small iron ball in its centre is placed in a cup of water. 3.9 x 10-3kg of water in the cup is displaced and the volume of the ice cube is 4.0 x 10-6m3. Ice density: 1000 kg m-3 Iron density: 7800 kg m-3, what is the volume of the iron?


What are the similarities and differences between an elastic and an inelastic collision?


A ball is launched from ground level at 5m/s at an angle of 30 degrees above the horizontal. What is its height above ground level at the highest point in its trajectory?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences