# Just wondering

asdf1
i'm interested in physics, but i don't major in it...
i look at physics in my free time, and i just came across the rutherford scattering formula and was wondering is it necessary to memorize it?

Staff Emeritus
Gold Member
Don't memorize it !

The important thing to take away from the formula is the $1/(1-cos \theta)^2$ dependence of the scattering cross-section which is a signature of scattering from point-like objects.

asdf1
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the rutherford scattering formula is
N(cita)=(NntZ^2*e^4)/{[(8pi*epsilon)^2]*(E^2)sin^4(cita/2)} right?
because i don't see 1/[1-cos(cita)]^2...

Mentor
Hint: browse through a list of trig identities.

asdf1
so sin^4(cita/2)=[1-cos^2(cita)]/2={1-[1+cos(2cita)]/2}/2?

Staff Emeritus
Gold Member
Sorry, I didn't make this clear earlier. I was referring to the differential cross section. That's a more useful form of the scattering equation.

asdf1
differential cross section? what's that?
@@

Staff Emeritus
It's the number of scattering events that go through an elemental area on the surface of a unit sphere centered on the scattering center. In spherical co-ordinates, an area element on the unit sphere (or an element of solid angle) is given by $d \Omega = sin \theta d \theta d \phi$.
The differential cross-section is $dN/d \Omega$