What is the significance of the E/M ratio in modern physics?

[sirous666]

What is importance of finding E/M?
I am doing a project on E/M and helmholtz coil. I heard that E/M is beginning of the Modern Physics. Can you tell me more about this experiment and why is it so important to know this ratio?
I also want to be refereed to some sources in which i can get whole a lot of information about this experiment and it's significance.
Please provide me with as much sources as you can.

 

[Matterwave]

By E/M do you mean electron's charge divided by the mass of the electron (usually denoted e/m)? e/m can be used to find some fundamental constants (e.g. e, or m), after some other experiments are made. e/m itself, I'm not sure has too much significance...

 

[Bob S]

First, the e/m experiment itself demonstrates the very important concept of a v x B (vector cross product) force on a charged particle in a Helmholtz coil. See attached thumbnail. The force on the electron is perpendicular to both its velocity and the magnetic field.

The measurement of e/m for electrons and protons was very important for determining the mass of the electron and proton (and other charged particles). But in order to get the mass, the charge had to be determined. So this is why Milliken's oil drop experiment (1913) was also so important. Knowing the electron mass from e/m and Milliken's measurement, the electron mass (actually mc²) could be used to calculate the Rydberg energy (13.6 eV) using the first quantum mechanical description (Bohr model) of the hydrogen atom. This could then be used to compare to laboratory measurements of the wavelength of observed atomic transitions (Balmer, Lyman, Paschen etc.).

Look up the url in the thumbnail for more information on the e/m experiment..

Bob S

 

[Matterwave]

Bob's answer is a lot better than mine...listen to him haha.