A stack of two transparent dielectric layers is deposited on glass ( )
PHYSICS · Single correct · A Level · Physics · Waves · Waves
Problem
A stack of two transparent dielectric layers is deposited on glass (n=1.80). The top layer A has index nA=1.25 and thickness tA=4λA. Directly beneath it is layer B with index nB=1.55 and thickness tB=4λB. Monochromatic light of wavelength λ0 in air is incident normally on the stack. Which statement best describes the reflected intensity at wavelength λ0 compared to that from bare glass?
(a) Reflection is increased because the two phase reversals make the reflected waves add in phase.
(b) Reflection is greatly reduced because the first two reflected waves cancel each other.
(c) Reflection is essentially unchanged because additional reflections from the lower interfaces exactly compensate any reduction.
(d) Reflection is increased only for wavelengths shorter than λ0 and decreased for longer wavelengths.