If two point sources that create circular waves are moved closer together, what happens to the spacing between the nodal and anti-nodal lines? a. the spacing increases. c. the spacing stays the same. b. the spacing decreases. d. none of the above.

The distance between the sources of a two point surface interference determines the number of lines that can be created for the nodal and anti-nodal lines. When the sources are moved closer together, the number of lines becomes minimal. Thus, the spaces between the lines become bigger. The answer to this item is letter A. The spacing increases.