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.

US
Answered by Umar S. Physics tutor

3985 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

What is the photoelectric effect?


Using Newton's law of universal gravitation, show that T^2 is proportional to r^3 (where T is the orbital period of a planet around a star, and r is the distance between them).


Experimentally, how would you calculate the Young's modulus of a material?


A motorist traveling at 10m/s, was able to bring his car to rest in a distance of 10m. If he had been traveling at 30m/s, in what distance could he bring his cart to rest using the same breaking force?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences