# Percentage transmittance gamma ray through lead

1. May 25, 2017

1. The problem statement, all variables and given/known data

2. Relevant equations
I = Io e^-ux

3. The attempt at a solution
0.75 = 1 * e^-u1
using algebra... u =2.117

I = 1 * e^-2.117*3
I = 0.00175

Answer is apparently 42.2. Can someone tell me where i went wrong? Thanks for any help as always

2. May 25, 2017

### Staff: Mentor

Check your math. When I put $e^{-2.117}$ into my calculator, I don't get 0.75.

3. May 25, 2017