# Homework Help: Find the power emitted (quantium mech)

1. Oct 16, 2011

### leonne

1. The problem statement, all variables and given/known data
consider a blackbody at t=7000 what is the power emitted through a hole 1m between$\lambda$= 4000 and 4001 angstrom

2. Relevant equations

P($\lambda$) d$\lambda$=A(2$\pi$hc2/$\lambda$5(......)d$\lambda$

3. The attempt at a solution
my question is the math, I thought u had to make a integral on both sides and have it go from 4000 to 4001, but the solution does not do this. they just plug in 4000 for $\lambda$ and for d$\lambda$ they have 10-10 Is both ways correct? I dont remember what i got when i did the integral
thanks

2. Oct 17, 2011

### susskind_leon

Strictly speaking, your way is "more correct". They use the fact that the range for lambda is very small and the expression is not going to change a lot. This way, the integration turns into a multiplication.

3. Oct 17, 2011

ok thanks