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.

BM
Answered by Ben M. Physics tutor

2537 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

Why does magnetic field do no work on an electric charge?


What is the maximum frequency photon of one of the photons produced when a electron and positron annihilate each other?


A basketball player throws his ball vertically upwards with an initial speed of v=40 m/s. Ignore air resistance. What is the speed of the ball at half of the maximum height?


How does having a rotating plate in a microwave help food to be heated eavenly?


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