# Second Nodal Lines

1. Feb 7, 2005

### Spyder22

Ok here's the problem:
Waves are produced by two point sources S and S' vibrating in phase. SEe the accompanying diagram. X is apoint on the second nodal line. The path difference SX - S'X is 4.5cm The wavelength of the waves is approxiately______.

 o X
|
|
`|
So------ o S'

I know what the answer is, but I really don't understand where this second nodal line would occur.

Last edited: Feb 7, 2005
2. Feb 8, 2005

### Staff: Mentor

Nodal lines occur where the waves from the two sources destructively interfere. The first nodal line occurs where the path difference equals $\lambda/2$, the second occurs where the path difference equals $3/2 \lambda$, etc.

So the second nodal line is the set of all points that are $3/2 \lambda$ closer to one source than the other. (Note that there are two nodal lines for each path difference: one on either side of the central antinodal line, which is a straight line bisecting the line between the sources.) This set of points forms a hyperbola.

You might find this site helpful: http://www.glenbrook.k12.il.us/gbssci/phys/Class/light/u12l3b.html