The Life Cycle of the Stars
Ideas in Physics
On this page you can read about a few different interesting experiments, or pieces of equipment, in the world of physics.
Electron Diffraction
This experiment uses an electron gun to essentially fire electrons at a graphite screen. Here, the electrons are diffracted through the small gaps between the carbon atoms in graphite and produce an interference pattern.
The seperation of the rings can be used to determine the spacing between the carbon atoms using Bragg's Law:
Where, d is the diameter of one ring, lambda is the wavelength, and sin(theta) is the angle of diffraction. With n being the integer representing the ring we are working with.
This experiment provides yet more evidence of the wavelike properties of electrons.
The Frank-Hertz Experiment
The Frank-Hertz experiment yet again serves as more evidence for the wavelike properties of particles.
Electrons are fired towards a positivly charged grid, inside a mecury vapour. At the far end of a chamber is a detector designed to measure the curent in the system, which will only be detected if electrons hit it.
At specific voltages the current drops, as seen in the image to the left this happens roughly every 5eV. This shows that the mecury atoms are only becoming excited at certain energy levels, just as electrons do.
Electron Microscope
A scanning electron microscope or SEM works uses high energy electrons to create a signal at the surface of solid specimens. In this way we can finely plot minute textures and crystalline properties of the structures and specimens we choose to observe.
Specimens must be coated in a conductive material to allow the electrons to do their job.
The magnification level of SEMs can range from 20x to 30000x!
Surrounding are three images taken using a SEM. There is the tip of a drawing pin, a piece of paper towel, and the surface of a ball bearing. Can you guess which each one is? Click on the image for more details.
