Two circular loops of wire, each containing a single turn, have the same radius of 4.00 cm and a common center. The planes of the loops are perpendicular. Each carries a current of 2.50 A. What is the magnitude of the net magnetic field at the common center

Lexy is correct because angle r is between the incident wave,  n  = 0, and a diffracted wave.

How is it possible that phylogenies based on sequences from nuclear genomes and organellar genomes (i.e., chloroplasts and mitochondria) from the same group of species yield phylogenetic trees with different branching orders?   answer :   the genome of the endosymbiont is more closely related to members of the group in which it originally evolved, while the nuclear genome of the engulfing organism has its own evolutionary trajectory.