What's next?
Monday 23 June 2025
Summer is almost upon us and we have started to draw up our “to do” list of improvements that we would like to bring to the site over the coming months. Obviously we have to choose the discussion topics for the silent podcast and audit all the links on the site. Once the examination results have been published, we will be reviewing all the recent examinations in physics and seeing what lessons we can learn for the future. We would love to hear from you if you have any other suggestions - just add a comment to this blog.
The A to Z of concepts continues to grow albeit slowly. Four additions to the letter B were added today: Background radiation, Back emf, Blackbody radiation, Boltzmann's constant. By way of a taster, the content for Black Body Radiation is copied below. It would be great to receive your comments and/or suggestions about any concept entries that you would like to see included in the future.
We will be reviewing all the recent Physics examinations after the results have been published. Please add a comment below to this blog if you have things you would like to discuss….
Blackbody radiation
All objects with a temperature above zero kelvin radiate electromagnetic energy. Objects also receive energy that has been radiated by other objects. Without an additional source of energy, the temperature of an object will be constant if the rate at which it radiates energy is equal to the rate at which it receives energy.
The absorption of radiation and the emission of radiation from a surface are linked together. Objects that are good at absorbing radiation are also good at emitting radiation. A black surface is particularly good at absorbing radiation (as all colours of light will be absorbed) so this surface is also a good emitter. The theoretical “perfect” absorber is called a blackbody meaning that the “perfect” emitter is also a blackbody. The spectrum emitted by this “perfect” emitter is called blackbody radiation. A graph of the variation of intensity emitted with wavelength of emitted radiation is shown below. The intensity is the power received per unit surface area of the receiving body.
Things to note include:
- The Intensity of the emitted spectrum depends on the temperature of the blackbody.
- The graph is constructed so that that area under any portion of the graph is proportional to the total intensity radiated in that wavelength range.
- Higher temperature objects emit a greater intensity of radiation.
- The peak wavelength of the emitted radiation depends on the temperature of the blackbody. The higher the temperature, the shorter the peak wavelength.
For more detail, research the Stefan-Boltzmann law and Wein's law