Answer:185.18 meV/m
Step-by-step explanation:
Energy loss for charge particle is given by
\frac{\mathrm{d} E}{\mathrm{d} x}\propto \frac{\rho Zz^2}{A}
where
\frac{\mathrm{d} E}{\mathrm{d} x} Energy loss per unit length
\rho density
Z atomic number
A atomic mass
z charge of incident particle(for proton it is 1)
For graphite
Z=6
A=12
For gaseous nitrogen
Z=7
A=14
![\frac{\mathrm{d} E}{\mathrm{d} x}=(k\rho Z)/(A)](https://img.qammunity.org/2020/formulas/physics/college/6wdlho0cy36fmnyen032w8n23uq8chjslu.png)
For graphite
![32.3=(k* 2.25* 10^2* 6)/(12)--1](https://img.qammunity.org/2020/formulas/physics/college/6ydsfk5m72yi521hhe4klujkioni5wkcay.png)
![E'=(k* 1.29* 7)/(14)---2](https://img.qammunity.org/2020/formulas/physics/college/hv8vmvvdrk8k8bnwueukf0p20fjozgiw4s.png)
Divide 1 and 2
![(32.3)/(E')=(2.25* 10^2* 6* 14)/(12* 7* 1.29)](https://img.qammunity.org/2020/formulas/physics/college/kpe9zym1y5new7d20w2qdyer68dy4btzrh.png)
E'=185.18 MeV/m