Type-B optical flat is tested for parallelism. What is the formula for the difference of the thickness of the flat at 2 points on the adjacent fringe? (¬¨¬®¬¨¬µ is the refractive index)$#

‚âà√≠¬¨‚Ñ¢/4*(¬¨¬®¬¨¬µ) microns

‚âà√≠¬¨‚Ñ¢/2*(1/¬¨¬®¬¨¬µ) microns

‚âà√≠¬¨‚Ñ¢*¬¨¬®¬¨¬µ microns

‚âà√≠¬¨‚Ñ¢*(¬¨¬®¬¨¬µ/2) microns

Type-B optical flat is tested for parallelism. What is the formula for

1.	Type-B optical flat is tested for parallelism. What is the formula for the difference of the thickness of the flat at 2 points on the adjacent fringe? (¬¨¬®¬¨¬µ is the refractive index)$#
A.	‚âà√≠¬¨‚Ñ¢/2*(1/¬¨¬®¬¨¬µ) microns
B.	‚âà√≠¬¨‚Ñ¢/4*(¬¨¬®¬¨¬µ) microns
C.	‚âà√≠¬¨‚Ñ¢*¬¨¬®¬¨¬µ microns
D.	‚âà√≠¬¨‚Ñ¢*(¬¨¬®¬¨¬µ/2) microns
Answer» B. ‚âà√≠¬¨‚Ñ¢/4*(¬¨¬®¬¨¬µ) microns