A Thin Sheet of Plastic (N = 1 $\lambda$ = 700 Nm)losses

Multiple Choice

A thin sheet of plastic (n = 1.60) is inserted between two panes of glass to reduce infrared ( $\lambda$ = 700 nm) losses.What thickness (in nm) is necessary to produce constructive interference in the reflected infrared radiation?

A) 218
B) 109
C) 55
D) 318
E) 443