Question

Calculus Based Physics

Physics For Scientists And Engineers withModern Physics (7th)by Serway, Jewett

46

55AP

6/10/2010 at 11:55:00 AM

Question Details: Ans. given below isnotadequate.

problem 55 ch 46 page 1390 asks for "the upper limit thattheobservation sets on the mass of a neutrino".

Obs. was a supernova 170 000 ly away.

8 neutrinos in 6s, (energies betw. 8 MeV and 40 MeV)

and 11 n's in 13 s ( 10 MeV n. needs 10 s more than photontotravel this distance)

The expert solution does not give this ans.

It only converts light years to seconds!

The book gives the ans. as " 19 eV/(c squared)"

Please explain this ans.

Brian.

Response Details:

19eV is energy in electron volts. 1 electron volt is1.6e-19Joules, so for very small energies it is more convenient touse theelectron volt rather than Joules.

From Einstein's equation e=mc*c, the solution you gave hasjustrearranged this to m=e/c*c

Was this what you needed clarification on?

My Response Details:

That is true but does this give the ans. 19 eV/c*c ?

m = e/c*c

m= 1.6 e -19/c*c but this is not = 19??

Sorry this is wrong. I have confused e for energy with eforelectronic charge.

Energy was 10 MeV,so m = 10 e^6/c*c.

This is still not = 19/c*c.

Please show how to get 19/c*c.

Brian.