# Just wondering

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?

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Gokul43201
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.

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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...

jtbell
Mentor
Hint: browse through a list of trig identities. so sin^4(cita/2)=[1-cos^2(cita)]/2={1-[1+cos(2cita)]/2}/2?

Gokul43201
Staff Emeritus
Gold Member
Sorry, I didn't make this clear earlier. I was refering to the differential cross section. That's a more useful form of the scattering equation.

differential cross section? what's that?
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Gokul43201
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 $dN/d \Omega$