# Homework Help: Boundary Condition querries.

1. Oct 5, 2008

### kloong

Urgent: Boundary Condition querries.

1. The problem statement, all variables and given/known data
Question given: A dielectric interface is described by 4y+3z=12. The side including the origin is free space and its electric flux density, D=ax+3ay+2az (micro) C/m2. On the other side, (Epsilon)r2 = 2. Find D2.

2. Relevant equations

3. The attempt at a solution
Ok, so this is how i try to solve it:
1. I get the unit vector of the equation given(but only make use of 4y + 3z).

2. Then i get the E1. (by using the eq D=(eps)E) thus getting: (ax+3ay+2az)(micro)eps^-1.
>> is it correct? because i am familiar doing it with E and not D. am i suppose to do it this way? or are there any better alternate ways?

3. Then i went on to get E1n by using the equation (E . an)(an).

4. Then E1t. (E1 = E1n + E1t)

5. Then E2n ( (Eps)r1 E1n = (Eps)r2 E2n) )

6. And finally, E2 = E2n + E2t. And using the eq D=(eps)E to get D2.

thank you.

Last edited: Oct 5, 2008
2. Oct 5, 2008

### HallsofIvy

One thing I see missing from all this is what the QUESTION itself is! What exactly are you trying to find?

3. Oct 5, 2008

### kloong

the second step. if it is correct if i change the given D to E1 using the equation D=(eps)E.

apart from that, i want to know if my way of doing it is correct or not.