How do we know the energy of a photon (light particle) is quantised?

Firstly, quantisation of energy means that energy can only exist for specific, discrete values, i.e. it is not continuous. Now, photons display this phenomena however it is not immediately obvious why, as in classical physics, we observe that light acts as a wave. To understand how the we know these particles are quantised we have to investigate a some practical examples. One of these examples is called the photoelectric effect. This is where a electromagnetic radiation (light) is incident on a metal. This causes electrons to become excited and thus jump out of the metal under certain conditions. However as the intensity of the light increases the energy of the electrons does not, leading us to believe that the light is not behaving as a classical wave as first thought. Furthermore, we observe that no electrons are emitted if the frequency of the light is below a certain value, called the work function. These two observations lead us to draw the conclusion that light, in this experiment, is acting a particles of discrete energy.

Answered by Ben M. Physics tutor

2395 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

If the force between two point charges of charge 'Q1' and 'Q2' which are a distance 'r' apart is 'F' then what would the force be if the charge of 'Q1' is tripled and the distance between them doubled?


What is the escape velocity of an object leaving a planet mass M, radius R?


What is a potential divider?


Explain how a standing wave is set up on a string fixed at both ends.


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