Two Flat Glass Plates Are in Contact Along One End

Multiple Choice

Two flat glass plates are in contact along one end and are separated by a sheet of paper 3.3 × 10−⁶ m thick at the other end.The top plate is illuminated by a monochromatic light source of wavelength 514 nm.How many dark parallel bands will be evident across the top plate? (1 nm = 10−⁹ m)

A) 7
B) 11
C) 6
D) 13
E) 9