Physics Formulas

Photon Physics Example

What is a photon?

A photon is a wave packet of energy such as in electromagnet radiation.

Below is an illustration of the relationship between E, the energy of a photon and its wavelength which is:

Energy of Photon relation to its wavelength

where E is measured in J and the wavelength is measured in nm.

Energy of the Photon proof

If two metal electrodes A and B are sealed into an evacuated glass envelope and a potential difference V, measured using the voltmeter, is applied between them as shown below.

Photon circuit

B is then illuminated with monochromatic light of wavelength 365 nm and I, the current in the circuit, is measured for various values of V. The results are shown below.

Photon question chart

From this graph, deduce the p.d. required to stop photoelectric emission from B.

Photon question

Calculate the maximum kinetic energy of the photoelectrons.

maximum kinetic energy