Light of Frequency 6

Light of frequency 6.00 × 10¹⁴ Hz illuminates a soap film (n = 1.33) having air on both sides of it.When viewing the film by reflected light,what is the minimum thickness of the film that will give an interference maximum when the light is incident normally on it?

A) 24.0 nm
B) 94.0 nm
C) 188 nm
D) 279 nm
E) 376 nm